Yep. Author here - that article is out of date now. I should really do a followup. Performance of CRDTs has improved again through a new grab bag of tricks. I’ve also been told the beta of automerge 3 uses a lot of the optimisations in that post, and it’s now much faster as a result.
A crdt library should be able to handle millions of changes per second. If it’s the bottleneck, something somewhere has gone wrong.
See: https://josephg.com/blog/crdts-go-brrr/
(And even these optimizations are nascent. It can still get so much better.)
The section you quoted describes an effect of homomorphic encryption alone.
There is the problem that both CRDTs and encryption add some overhead, and the overhead is additive when use together. But I can’t tell if that is the point you are trying to make.