No it's a great exercise i think, doing so you can see what shapes the artists use, what proportions, and you might try them later, it's really fun to play around with different proportions etc ! But you need to focus on that
I think if you're still focussed on anatomy its better to stick to real models
If it's a style exercise then sure go ahead and study other artists' way of drawing the anatomy !
Both are good exercise but different goal I think !
But the most important thing is be sure to actually learn from them, don't just trace and think it's gonna be useful, that's why marc's made a video about observation skill being the most important !
Good luck with those 