You could still apply Group Policy’s to later versions of IE as well. So that wasn’t the reason. It was more to do with corporate apps being tied to specific versions of IE due to later versions of IE having breaking changes in the way it rendered content vs earlier versions of IE.

Those of us who remember web development in the 90s and early 00s will vouch for how the pain wasn’t just supporting different rendering engines, but even different versions of the same rendering engine.