English isn’t my first language too (its third in fact). Doesn’t support COULD mean several things, depending on the context. In example games never designed for Linux work through Proton. Developers may not support it, but game might work perfectly fine. In context to the Input system, not supporting here means that Valve does not help and doesn’t make creating sequences of inputs easy. This at least puts Valve in a position where they can say this wasn’t designed as a cheat program.