It is true, but occasionally it is a practice in some companies with certain business models to leave part of users contributions free up to the users to decide. I have bought some games from their preservation program, and gave me the option to add some extra donation for the project, which I did. I guess this is similar to that.

Moreover, if somebody is really into these old games, they may want to support it and get access to the behind the scenes material, discord, vote for which games to prioritize etc. I don't think this is very different than eg subscribing to the patreon of a creator to get some extra content.