Its already really rare for an ico to have a product that investors can test, playkey can already be tested by people who want to see the performance of game on the actual platform. Its really a good point, investors always enjoy to see that there is already something for the project and to see the project is in good way of development.
Actually, people can already see how the games perform by watching demos/reviews of the game, and if they actually want to play it on Playkey then they need to buy it on Steam. I'm still very positive on this project though, because most people would only use their funds to purchase games which have good reviews.