"App stores" is generic term. If you are looking at mobile, I'm sure the number is more than 50%. There is no possible way that 50% of Windows apps come from the Windows store.
Would seem unlikely that they have blocked it just for using Electron as they are using Electron for newer apps such as Microsoft Teams and Azure Storage Explorer.
Surely then you're not the only one who would speak up. Also, if an app isn't browsing the web, but is written in Electron (many fall into this category) then it would be unaffected by this policy.
So at the very least your title should be "Microsoft Policies Blocking Electron Apps That Browse the Web". But I understand that doesn't generate as many clicks.
Who uses the Windows store, anyway?