1. Common code format across the Power platform, and

2. the branding MS was using to describe everything that would be put under source control.

I have some doubts about whether the second point is true.

This article (https://docs.microsoft.com/en-us/power-platform/power-fx/ove...) discuss PowerFX stored as YAML files under source control.

And this article which predates the PowerFX announcement (https://powerapps.microsoft.com/en-us/blog/source-code-files...) discusses UI YAML files under source control.

But nowhere does it say that they are branding the UI YAML files under the PowerFX moniker.