"Expected to" is definitely going too far. The Japanese had regular supply establishments, including food distribution and depots, and well understood logistics, including that troops need to be fed regularly in order to be effective.

That said, Japan's merchant marine was a bit below adequate at the start of the war, and while the military did take up several ships for military shipping, Japan was very reliant on sea transport and cutting too far into the civilian shipping would have deranged their economy.

Plans may not survive contact with the enemy, and that includes supply plans. Japan's strategy of occupying a large number of outlying islands meant that they had to shuttle food and supplies out to those islands, and that left their shipping open to attack. While the American and British navies had as a major duty escorting the sea freight of those nations, Japan did much less of this - their destroyers were built and trained as part of their offensive effort and commerce protection was far down the list of their priorities. (Evans and Peattie talk about Japanese naval priorities and their reasoning in Kaigun, a wonderful reference for anyone interested in the history of the Japanese navy.)

US anti-commerce efforts didn't bear a lot of fruit at first (defective torpedoes meant that very few kills were made by US submarines), but as the US started moving into the Solomons, the Japanese were increasingly faced with the task of moving supplies to their troops in combat zones where they didn't have control of the sea. The Japanese tried to move supplies in by night (but the supply ships were often subjected to air attack the previous or next day), and also ferried a lot of supplies in destroyers (fast and hard to hit from the air, but with limited cargo capacity.) Submarines were occasionally used, but they had neither speed nor cargo capacity, and can be seen as more of a measure of Japanese desperation.

As the war progressed, the Japanese suffered more and more shipping casualties and keeping their outposts supplied became more difficult. Many of their garrisons were bypassed and left isolated, and simply didn't have any choice but to supplement their diets however they could; this didn't represent Japanese policy per se, just their inability to force through supply runs in the teeth of Allied naval and air forces. (Note that eventually starvation problems also occurred even in the home islands, with the general ration having been below 1000 calories per day in 1945.)

This didn't affect the Navy as much (by which I mean actual sailors; naval base personnel suffered and starved (and fought, as scratch infantry formations) along with the Army. But the ships needed fuel. You can put men on short rations for a while, but you need to burn fuel in order to move ships, and so keeping the fleet fueled was a very high priority for the Japanese navy. Compared to the problem of moving around thousands of gallons of petrochemicals, keeping the actual sailors fed wasn't a big problem. And as the war progressed, the Japanese navy was tied more and more to its bases - lack of fuel kept them from sailing, but it also kept them where the supplies were.

Note that this sort of thing didn't materially affect what kind of service you'd pick, because Japan wasn't precisely forthcoming about its losses with its civilian population; the man on the street didn't know about the horrible starvation among isolated Japanese forces in Guadalcanal or New Guinea. So nobody expected that they'd be reduced to foraging for roots before joining up, as it were.

There's an interesting question behind this, though. I know that the US navy tended to eat better than the army (there were a lot of "dual standard of living" comments), but how did peacetime Japanese army versus navy vittles compare?