Once 5.0 becomes Last-LTS, the canThrowSSVOnIgnored field should be removed from ChunkVersion: https://github.com/mongodb/mongo/search?q=SERVER-53099&type=Code

It was added in 4.4 in order to be able to safely communicate with 4.2 binaries. It is needed in 5.0, but is always sent as true and never consulted (this ensures that upgrade from 4.4 -> 5.0 will still work) and in the next LTS release it will not be necessary.