I didn't learn any anatomy or physiology in art school and don't see it as absolutely necessary.
It's only necessary if it is necessary to your artistic goals. I was always obsessed with drawing the human figure so I felt such studies were quite useful. I didn't use this knowledge much while working in an Expressionistic manner. Even my current body of work employed simplified figures that didn't require a great deal of anatomy and/or physiology. More recently, I have become more interested in muscular figures and dancers... figures in motion... and I am again making more of an effort in studying anatomy and physiology.
One should just keep in mind that artistic anatomy is not quite the same thing as medical anatomy, and it needs to be applied to drawing. A lot of art books take what seems to me like a quite wrong-headed approach to the subject. Years ago I did what I thought one should do: copied from anatomy books. It did not help me in the least with figure drawing, so for many years I completely gave up on anatomy. More recently, I found more productive ways to study anatomy, but I found that for my purposes, I do not need a great deal of it. Those artist's anatomy books that have detailed pictures of individual vertebrae and ribs and so on are probably overdoing it, even if you want to take a highly anatomical approach.
But another thing I found is that studying anatomy to some extent tells you what kind of art you want to do. If you want to emulate the Renaissance masters, or those guys who do superhero figures for Marvel, you will probably almost automatically have a far greater interest in anatomy than if you want to follow in the footsteps of Van Gogh, or, like me, you are happy with cartoonish kind of work. Now if your initial ambition is to go work for Marvel, but you find that the required anatomy bores you, it may mean you should reassess what it is you want to do.
But at least some anatomy really does come in very handy. I have been following a bloke on YouTube who is into nature journaling and drawing animals, and in some of his videos he looks into the anatomy of specific animals, but he does so purely from the point of view of artistic utility. He also makes a point of showing, via photos, how the internal anatomy he discusses influences the outward appearance, and how it can help one to draw more accurately. It's brilliant stuff and has been tremendously useful to me. Far more so than some of those thick Bibles of animal anatomy that show you every single muscle and bone, irrespective of whether they make any real difference to what the animal looks like.
Of course, anatomy might also interest one from the scientific point of view, which is perfectly valid, but one should not confuse that with its artistic utility.
I am not much good at figure drawing, but personally, I found what helped me the most, far more than pretty much anything and everything else combined, has been gesture drawing. But then, I am more into somewhat cartoonish drawing, where gesture is obviously more important.
We can probably say that no body of knowledge or artistic skill is necessary to create art of real merit. Perspective, proportions, color theory, paint manipulation, drawing from observation... an artist can get by without any of these. I would argue, however, that the more knowledge you have and the more skills that you have mastered the more possibilities are open to you.
Yes, indeed, and one need not worry that it will prevent originality or somehow contaminate one with conventional ideas or whatever. Even a casual look at a great many of Picasso's drawings and paintings will show you that the ARC assessment, namely that he had no skills, is quite wrong: it's pretty obvious that he was thoroughly versed in traditional art skills, including anatomy. I.e. his very traditional training did not prevent him from being original and creative. On the contrary, I think his knowledge of basic skills facilitated his more adventurous work.
Where did the guy find the time in between all his paintings and his diplomatic efforts?
