That's a good point. This certainty is not about trying to exclude people on purpose. I actually tried to think of a ways to make the system as fair as possible. Here are some solutions that I thought about and why I felt they would not work:
1. Solution idea: any game type can be submitted. Problem: someone cannot participate because the last person has linux (just random example of rare platform) game and they do have linux machine to test the game with. In worst case this could block the whole system from proceeding if no tester comes who would have linux.
2. Solution idea: any game type can be submitted but if you cannot test certain game you are allowed to skip testing it. Problem: someone puts their link in and reviews 2 games but neither person will review them back because neither of them do not have a linux (again, nothing against linux it was just my running example). I fear that this would be even crueler fate than just being upfront told that not all games can be promised testing.
3. Solution idea: only web games allowed. Problem: What about people with non web games? But adding them leads back to the situations 1 and 2.
In the end I went with solution 4: only web or cross platform games. My idea was that it would be the most clear division without having other issues than that it unfortunately excludes some people.
I would like this to be as including as possible, so if you have other ideas to think about I would be happy to hear suggestions. Otherwise, at least one new solution idea that I thought about now that you brought this up would be to just setup different topics for each major platform. And then Windows game creators could review each others game in one topic and linux game creators could review each others game in another topic. Would you feel that it would work as a solution? I could setup something like that if you like.