Thanks for the clarifications, this does perfectly answer my questions. I would consider though that the differences between the different formats of the dumps are minor, even if the processes are independent but this is indeed interesting to highlight, I don't think many people are aware of this.

While this issue is supposed to be closed, one can still see at https://dumps.wikimedia.org/wikidatawiki/entities/20210628/ a "-all-BETA" dumps (in .nt and .ttl formats) and a -all.json format dump. Is it normal? Can you please confirm that the content of those dumps is the same except for the serialization format?