I think it depends largely on what perspective you are viewing this from, and I would love to hear a comment from a European medievalist on how this was viewed at the time in France or Europe, but I think the line you quoted is broadly in line with the thinking of historians of the Arab conquests.

That's largely because the broad conclusion is that the Islamic empire was incapable of expanding very far beyond its borders in 732 and that had the Arabs won at Tours it would not actually have changed the situation very much.

That sounds like a counterfactual but it has some good supporting evidence, namely:

1. In 750 the Ummayad dynasty was replaced as rulers of the Arab/Islamic empire in the Abbasid revolution. The internal violence of this revolution, within a matter of decades, led to some significant fracturing of the empire, especially at the periphery in North Africa and in Islamic Spain. The survivors of the Ummayad dynasty escaped the slaughter of the Abbasid Caliph al-Saffah and established their rule in an independent Islamic Spain, which would have been the logical jumping off point for any renewed expansion into Europe. In fact they proved incapable of doing so and as a peripheral kingdom of Islamdom they could not muster the kind of forces that were available to the Abbasids. And if the Abbasids wanted to expand in that direction (which they did not) they could only have done so by going through the Ummayads, not to mention the other independent dynasties that would pop up in North Africa.

2. Contrast the loss at Tours in 732 to the victory at Talas in 751. Despite crushing the Chinese army of the Song dynasty, the result of the battle was not massive civilizational change or Islamicization of China, rather it was the consolidation of Arab/Islamic control over their central Asian territories.

3. Given the above, and the eventual reconquista of Spain, it strains credulity that an Islamic conquest of France, let alone all of Western Europe, was ever possible.

I think the conclusion is that that Tours was important as a high water mark, but a high water mark that was going to turn back somewhere or other. If the Arabs had won at Tours, it's difficult to imagine them continuing their victories for much longer, and nearly impossible to imagine that they would somehow have wiped out European civilization or something (not that the Europeans were very civilized at this point, but that's a separate issue!)

Adding onto this, would you say that the sieges of Constantinople in 674 (although I've read claims that there was no siege in 674...) and later the 2nd siege in 717 was a bigger battle in terms of containing Islamic conquests? Since if Constantinople fell the Islamic armies would have definitely crossed the Bosphorus

Had Martel lost, the important question is whether the Umayyads could have continued pressure into France. This becomes more likely if Martel had died in battle.

Had Martel died at Tours, that would leave Carloman and Pepin leading the Franks at around 20-26 and 18, rather than 15 years later when Martel actually died.

If Pepin doesn't keep power as Mayor of the Palace and Carloman doesn't retire to a monastery early, it's possible Charlemagne never rules. That completely changes the long term power balance in the area.

Please keep in mind that due to the fact that this is disputed, no one is going to be able to give you a definitive answer. Scholars differ on this.

Both opinions have good supporting evidence so at the end of the day you can only read the arguments presented and make your own mind up.

I personally believe that if Charles Martel was defeated it would've opened the door to more incursions, and a greater islamic presence on the other side of the Pyrenees.