Not entirely true. Actors are big (about 2KB) while plain object is less than 300 bytes.
Using actor just for the replication is just wasteful. If something doesn’t need physical representation in world, but you still need reflection and polymorphism, UObjects are very good choice for replication. The only cevat is that you have to replicate them trough actor or actor component. But that’s not really hard.
Unless the you only have very few replicated actors, then whatever. For anything more than 20 I would think twice.