Yep... It's not as if developers can actually know ahead of time *exactly* how much a certain feature will cost to develop (things often take longer than expected in game development). It isn't an exact science, it's a lot of trial & error; sometimes things sound great on paper but when the developers actually create a prototype build they find that things just don't work or aren't enjoyable, so they have to scrap it and try a different approach. So it is always good for a developer to have "extra" money in their budget, because time is money.
This is why you see so many Kickstarters where developers get themselves into trouble with the feature creep caused by stretch goals where they underestimated how long things would take. (For example, Larian ended up not fulfilling about half of their stretch goals for Divinity Original Sin. as they found things like NPC schedules would create too many new bugs and issues to fix.)
However since this is now Harebrained Schemes third Shadowrun game, and they are using an improved version of the game engine they built, they probably have a more accurate estimate of how much certain features will cost to implement than developers who are creating everything from scratch. Which is why they aren't going crazy and promising every single requested feature, because they know as awesome as it would be to have things like a full fledged stealth system and Astral space, it would cost a lot to do it right.
I created a GOG wishlist entry. I think it is basically guaranteed the game will sell on GOG, but hey, it's fun to vote for things:
http://www.gog.com/wishlist/games/shadowrun_hong_kong