It defeats the purpose of using it. There's plenty of unlocked bootloader OS that make root easier. Calyx or lineage work better for root. If it works well for you though, great!
Not entirely, there would be a bit more security during bootup.
However, the risks and problems are probably not worth it.
Other benefits Graphene advertizes: they are much better and quicker applying updates (that's easy because they only support pixels), they allegedly support much more and better exploitation mitigation mechanisms, and have a Google Services sandbox that looks quite interesting.
Though, after the conversations I had with them I really do not want to trust those people :(
The usual: Voice some opinion that doesn't exactly match theirs, Ina friendly way, get insulted, get accused to be part of another group that allegedly is conspiring to harm them...
Later found this is apparently a pattern and happened to others in a very similar way, e.g. https://m.youtube.com/watch?v=4To-F6W1NT0
Hey there. GrapheneOS community moderator here. In case you haven't taken a look, I would recommend reading through https://grapheneos.org/features to get a better sense of what GrapheneOS provides beyond what you mention above.
I also wanted to address a few things:
Applying updates quickly is extremely important. You seem to consider GrapheneOS supporting devices that get timely updates and make developing for them easier to be "cheating", for some reason. Regardless, every GrapheneOS change has to be ported to each monthly, quarterly and yearly release of Android, which isn't a trivial task, as I'm sure you can imagine, but it's done correctly and quickly, because it's important.
Now, I also wanted to address the last part of your comment here, because judging from your other comments in these thread, you seem to have a bone to pick with the project and its team. It's unfortunate that a lot of the time, project members and community members taking the time to properly answer questions and explaining how things work is seen as a bad thing because it is not the thing that you (or anyone else, I'm just using you as an example here) wanted to hear. The team considers it very important to help people understand how things work, as there is unfortunately a lot of misinformation about these topics. The fact that we're passionate about explaining how these things work, and the fact that it clashes with people's preconceived notions about things often means they're hostile in return, which is unfortunate, but still, it is important.