I pondered the same point. If YC community isn't your target market, then this benefit is also of limited use or worse, damaging via creating illusion of demand which evaporates when you hit your target market.
You need to think of it as product development. It's hard to get users to use a product that no one has heard of. The YC network will actually try it out. This is important because even if they aren't your target market, it's still use of the product - which will always teach you something.
If the things you learn from YC community usage is inapplicable to your target market, then that is not useful learning. It is useful for business if their use context overlaps with that of your target base.