Yes, but if Apple's complaint is truly about security then they should have blocked it even harder before, because the cloud version wasn't E2EE. Their behavior reveals that security is not their real concern here.
Structurally, the cloud version was you logging into your iMessage account on a friend's computer. How could Apple possibly prevent that?
I think it actually makes a pretty strong case for Apple opening up a better interface that lets people achieve the same outcome they clearly desire so much, they'd even compromise their own security to achieve it.
Apple had plenty of ways to detect a datacenter full of Mac minis logging into iMessage accounts from all over the world, multiple on each machine, with custom software automating message sending, which I believe is even open source so Apple could look at it.
