He’s right, 2D and 3D are very different, BUT: drawing can help you out in many ways. Consider: learning anatomy often involves reading books and memorizing things. If you learn it by drawing it, however, you’ll have a visual memory and you’ll learn a lot about its 3-D shape. It’ll make it easier to remember because anatomy will mean something, it’ll have substance. One can never be good enough at drawing, so keep practicing!
3D obviously takes practice, too. I come from an opposite background-- I’m not very experienced in hard-body modelling, but I have spent the bulk of my time modelling organically since I started using Blender. You should practice organic modelling because it’s so difficult. What you’ll learn about topology and the essentials of modelling will stay with you when you do hardbody models, and you’ll notice them improving, too. And it does take practice, you learn more and you get better every time you do it, and you can always try new things to see if they work. Controlling edge flow has become so much easier since I made two or three each of hands, faces, feet, etc. (But then I’m still no expert), and that always helps when I try to make hardbody meshes, which (correct me if I’m wrong here) has less strict “rules” as organic meshes (which have to animate, after all!).
Some things to keep in mind:
Topology (edgeflow, basically the ‘flow’ of the surface of an object) should follow the muscles/anatomy of the subject. Even a car has some “anatomy,” so this goes a pretty long way. This series should help: https://vimeo.com/cgcookie/videos/search:topology%20overview/sort:date
Quads are (as always) preferable to triangles and ngons. In organic modelling, you use quads because they subdivide and smooth correctly, so don’t introduce triangles unless you know what you’re doing-- they’ll screw up the ‘flow’ and make the subdivision surface ugly. Never use ngons, they can (and should) be turned into quads and triangles. This isn’t an absolute rule, but it’s usually a good idea. The hours you’ll spend agonizing over how to make the mesh all quads will teach you a lot about how to control your model! Sorry for overusing italics!
And now, a tip: make sure every vertex has a purpose. If you don’t know what it’s for, it’s probably in the way. Each vertex should add some detail, somewhere. Often that means positioning them individually. But there’s a good reason-- too many vertices will make your mesh messy and hard to control. And as a bonus, simpler meshes are easier to rig and animate (less lag on the CPU!). Start simple before you go complex.
I recommend practicing topology on something simple, like a human torso-- the most complex part is the shoulder, which should only be a little too hard at first. Then you should move on probably to a face, they can be trouble but I think they’re easier than hands and feet. Ears, however, are a nightmare and will require you to break some of the “rules” I’ve laid out and generally make your life hard. So save those for last
Sorry for being so longwinded, this is a favorite subject of mind, and I think I’m pretty good at it.