It's really up to the corporation whether they think it will benefit them. I agree that Valve has so far not been hostile toward GE, and it looks like proton has a very permissive license, but if it were any other digital storefront, doing anything to allow users to consume your content without using your storefront would be seen as at attack on their bottom line.
I'm actually curious how this new standard would potentially benefit other storefronts who haven't natively supported Linux yet. If it's going to make things easier for existing open source launchers, then it would also make things easier for competing launchers. I know as a consumer, I want GOG, Epic, EA, etc. supporting Linux, but does valve? I don't know, maybe, maybe not. On the one hand, maybe they don't want competition in their niche space, on the other hand, maybe they'll do anything to take marketshare from msft.