So about some of the new things.

Question can you see an issue? 

https://www.dndbeyond.com/characters/173298565

Take your time, no homebrew, 100% DnDB purchased conent, plus drops. 

Spoiler: 

so to make this point clear as day. 

https://www.dndbeyond.com/characters/173300607

also in order to use a subclass feature, I had to add from Homebrew on this because someone at DnDB forgot to add Vestige Campanions to familar creatures. woot. /facepalm

Something similar has been possible ever since the release of the 5.5e core books, as it'll let you add both 5e and 5.5e versions of the same class to the same character if you turn off multiclass prerequisites. I doubt they're going to do anything about either issue; the whole point of allowing you to turn off the multiclass prerequisites is to let you do weird stuff that's outside the normal rules.

The Vestige doesn't show up in the Extras tab because it has dynamic stats. It's not that they "forgot", it's that the Extras tab doesn't support creatures that have stats that depend on the stats of their owner. It's similarly an issue with Beast Master Rangers, Battle Smith Artificers, and a whole bunch of summoning spells.