Sure, ripping stuff from games for private use may hurt no one, since it gives you endless resources to experiment with. Great tools all over the web for that.
BUT. . .
Folks spend endless hours making these models, and if they are ripped for commercial use, think of it as having a lovely family farm that is made useless by a few thousand squatters using your fields to live on.
You can always ask for permission to use models and ideas, if you cant make your own, or afford to buy some.

You are correct, and I'll add that "private use" does not in any way imply it's okay or legal at all - one must always read and understand the ToU, ToS, EUL, etc., etc.

If there is any doubt, don't use it.

Unless you have a really good copyright lawyer on retainer....