Yeah, grandparent is misremembering a real event. Steam did do a panicked reaction to Windows store: a hard pivot to Linux support and the linux-based SteamOS.

Steam was nowhere near the app store we know today when it was created. It was Valve's auto-updater and match-making service. They had a few partner games using it as well.

I may recall it badly but I am pretty sure they opened it to general companies and indie studios as a reaction to Windows 8 built-in app store:

https://www.bbc.com/news/technology-18996377

I've been on steam since a while after it's genesis. IIRC the store aspect of steam started in 2006-2007, which is way before even windows 8 which only came out after 2011-2012