If I program in one language for a few days, then it might take me an hour so so to get back in the groove of another language, and I might momentarily forget some syntax difference. For example, although GDScript looks more like Python than Lua, it allows an optional syntax for dictionary construction that is from Lua. If you learn that syntax while coding GDScript, well, you might try it when scripting Python and loose a couple seconds trying to figure out what you did wrong.
So if you mean "bad code" as in "I can't paste my GDScript directly into a Python editor", well, yes. Although I've done exactly this for some code snippets with only minor changes. If you mean "bad code" as in poor logic or poor programming practice, I don't think so.
I agree with the comment above that Godot might provide you a better goal-oriented learning environment than you can find elsewhere. Whatever it is that gets you to code is what will make you a better coder.