To help with future searches, it's Simon Webb, "The British Camps", Jacobin (magazine), 8 May 2017, https://www.jacobinmag.com/2017/05/uk-concentration-camps-wwii-poland-internment-prisoners .

I agree with your characterization of

what the article called 'concentration camps' and to my reading seems to equate them with Nazi camps, something which I find to be spurious.

The subtitle has "the British, not the Nazis, pioneered the concentration camp", as if the British in the Boer War were the first people in all of history to think of confining large classes of civilians in camps. Even off the top of my head, I could think of American imprisonment of entire Indian tribes, and putting them in reservations. Looking a bit more, there were Spanish camps against rebels in the late 1800s, and US camps in the Philippines after the takeover. Later, he wrote, "The British had been early adopters of these exceedingly useful establishments". Calling the British "pioneers" and "early adopters" in this form of inhumanity is a travesty of the truth.

He refers to all confinement as "concentration camps", regardless of purpose. And the examples he gave for Germany are Auschwitz, Buchenwald, [Belsen-]Belsen, and Dachau. Auschwitz was a complex of camps that held all that plus outright immediate extermination of over a million. Each of the others had tens of thousands dead, due to neglect, disease, deliberate working to death, or outright murder. Implicitly equating them with all other World War II camps, or other camps at other times, is highly tendentious.

I do not intend to defend most of these camps, either in their purpose or their implementations. Few had the nice conditions that P. G. Wodehouse eventually got. Even "camp university" of Hutchinson in the UK had guards who stole from and beat prisoners, and had Jewish refugees forced to share beds with Nazi sympathizers. Just off the top of my head, I also thought of the deplorable (or insert a stronger adjective) US internment camps against Japanese and Japanese-Americans. Mass death due to hunger, disease, or misery were common.

As for imprisoning Axis nationals in the UK in 1940,

Of course, no one wanted to call these new institutions "concentration camps", so they renamed them "internment camps" to differentiate them from the Nazis’ practice. But these camps also held people indefinitely and without trial because of their nationality, ethnicity, religion and/or political beliefs.

They were called "internment" because that became the term of international law. The term is in the Fourth Geneva Convention of 1949 (arts. 41-43), but that was after the war. I don't see provisions for civilians in the Hague Conventions or in the Geneva Convention of 1929. Provisions for internment of alien nationals goes all the way back to the original Magna Carta of 1205:

(41) All merchants may enter or leave England unharmed and without fear, and may stay or travel within it, by land or water, for purposes of trade, free from all illegal exactions, in accordance with ancient and lawful customs. This, however, does not apply in time of war to merchants from a country that is at war with us. Any such merchants found in our country at the outbreak of war shall be detained without injury to their persons or property, until we or our chief justice have discovered how our own merchants are being treated in the country at war with us. If our own merchants are safe they shall be safe too.

He refers to "385,000 enslaved workers" in the UK in May 1946, apparently largely working on farms, in apposition and therefore in comparison to "SS officers" facing trial. Note that he doesn't there say who they were, how they got there or why, and why "thousands more were arriving every week". Later, he calls them "German prisoners", again not being specific. Later, he finally gets around to noting that they were POWs, "So the United Kingdom changed their prisoners’ status from prisoners of war to surrendered enemy personnel" to evade Geneva Convention protections. One protection is adequate food and housing. But calling them "enslaved workers" -- had they been POWs, the Geneva Conventions explicitly say that captured enlisted personnel may be put to work in agriculture.

Also, why condemn just Britain, and not even mention the US's Disarmed Enemy Forces, or US and British "Japanese Surrendered Personnel" (to help the Dutch, the British even used them as military units against Indonesians!), or German reclassification of Polish and Yugoslav military personnel (on the grounds that the countries didn't exist and therefore there was no country for them to be POWs from), or Germany's "Italian military internees" (there was no war, so they couldn't be POWs)? And probably the Soviets did it too, and I just don't know the details.

To say that "everyone did it" does not excuse it. There's a reason why the 1949 revision of the Geneva Conventions attempted to close the loopholes. But it makes it more comprehensible, and indicates that the relentless slamming of the UK should be broadened. As written, the entire article is written to damn the United Kingdom, and almost only the United Kingdom.

In general, I would call this a very slanted attack with a substantial amount of falsehood and guilt by association.