Hypothetical here DM says that.
It's kinda clear what they mean what's not clear is where they draw the line.
Then it is incumbent on them to clarify where the line is. If you intend to exercise authority, you need to be clear.
This is why I always specify that:
- I support all genuine player enthusiasm, and I will bend over backwards to makethat happen.
- Enthusiasm is genuine when it is not exploitative, coercive, or abusive.
- "Exploitative" means using rules to break the game's spirit. Nigh-infinite damage, invulnerability from joining three highly specific features, etc.
- "Coercive" means manipulating others, mechanically (e.g. char-building) or thematically (e.g. "date my char because I'm sweet on you.")
- "Abusive" is hurtful, belittling, demeaning, etc. Making others feel bad, mocking, etc. This is relatively rare, but I've seen it.
- PLEASE TALK TO ME. I want your experience to be awesome. If you have an idea, any idea, run it past me. We can work it out if it's genuine.
I am a huge believer in supporting damn near anything the players want, so long as it isn't any of those three things (exploitative, coercive, abusive.) I'm not a pushover, I won't tolerate crappy behavior, but I will absolutely do everything short of compromising the spirit of the campaign and the other players' fun in order to see an idea come to fruition. It may take time, or involve a lot of work on the character's part, or be only a partial fulfillment, or require some serious re-thinking of exactly what it is/how it works/etc. But I will throw everything I have at making it happen, one way or another, because
that's how I earn my players' trust and respect.
There are a lot of DMs out there who think they simply
deserve player respect because they do world-building work, and that's simply not true. Just like how an author does not
deserve the respect of the reading public simply for doing the years of work it takes to create a solid manuscript and get it published. It is incumbent upon the creator to
demonstrate that the creation is worthy of the audience's time. For the DM, part of proving that you are worthy of the players' respect and trust lies in showing that you are willing to not just meet them halfway, but to walk a mile at their side, so that they'll be willing to walk a mile at yours.