First of all I want to clarify I’m not a lawyer.
Can you clarify what laws you’re referring to? I’ve never heard of that and it sounds like something I should read up on.
One example is, let’s say you have a refund policy that you will only refund customers if they’ve played for less than 4 hours. Now two customers that have played the game for 5 hours, request a refund from you. For whatever reason you were feeling kind and you refunded the first one, but decided to keep your policy on the second one and declined it. Depending on the country, this can bring you a lot of problems, but if the marketplace you use takes care of refunds for you, you don’t have to worry about it.
Another reason is, assuming you plan to publish on multiple stores, some of them have restrictions. For example you can’t sell your game for $5 on one place, and for $40 on another. If you start giving refunds because you want to be nice, you would be violating the rules of other marketplaces which have their own policy on refunds.
These are just examples, each country has their own laws which could be similar or entirely different.
Having a button as you described sure is possible, but it’s not really doing anything, it’s just for convenience, so it could be a thing. Although I’m not sure if it’s worth the time.
I respect that you want to be nice and give everyone refunds. This kindness is appreciated and I’m sure customers would love that. The reality is once you start selling games, you have to treat everyone consistently, regardless of how you feel.
Hope that makes sense. If you want more concrete examples of how the law works, I’d suggest to contact a professional. Or let Itch.io do its thing, since I’m sure they’ve already done that to some degree :)