I know there are concerns over how it isn’t “true open source” but it’s a hell of a lot more open than ReVanced.
For me, terms and definitions are very important. Just like right to repair is often misrepresented to the detriment of consumers, it’s important to only talk about open source if the license actually respects your freedom [1].
Open source has a lot of positive connotations and calling some project open source while only being source available feels like taking advantage of it.
It’s similar to how large corporations talking about being eco friendly with their packaging whilst making the actual devices as hard to repair as possible.
You’re right, the ReVanced project is open source, but the resulting app is not, since it’s modifying the official YouTube app.