Professor gave full credit for incompleteness
It seems an odd policy and, as a colleague, I'd be interested to know why he does this. But I wouldn't condemn it without more information.
However, if it is clear that he actually reads your work and comments on it when necessary to avoid having you develop misconceptions, then it might be fine. It is even possible that what you do provide makes it clear to him that you understand what needs to be understood. But it is hard to say.
If you got full marks by not trying at all, of course, then the standards are too low, but it seems to be a &quot;carrot but no stick&quot; approach.
But the fact that you are asking here seems to imply that you are conscientious, at least and if you get feedback when needed you will probably be fine. But, I think that asking about the teaching philosophy behind it is also fine.
It is also possible, I suppose, that he has a reading difficulty, the same as some students do, or is so occupied with things like research (or family) that he fails to notice things. That wouldn't be so fine.
But, as I've stressed in other answers here, the essence of learning is reinforcement and feedback. If you are getting that, then all should be well. Some people don't need to be graders in order to be good teachers. I wish there were more, to be honest.