I may be misinterpreting things, but I believe I have seen the following. Since the IMG changeover, I've bumped my energy (and mood) tank up to over 4,000. As usual, both energy and mood drop periodically regardless of activity. I believe this drop is greater than before, probably a percentage of the full tank. If I'm correct, then the downward force of mood is greater while the upward forces (petting, nibbling, etc) have remained the same. If find that simply maintaining 90% mood now is quite difficult, where previously it was fairly easy. A trip through the AL or drinking a Savory Smoothie has only part of the effect (percentage wise) that it formerly had.
I can't complain about the energy aspect, since energy at the bottom of the tank is just as valuable as energy at the top. But since mood level affects iMG rewards, it is significant.
Perhaps the Devs have thought about this and determined that the benefit of the bigger tank is greater than the need to do more mood maintenance. I dunno, but I'm curious first if my observations are correct and second if they've thought about this consequence.