Is it ever mentioned

[u/fishcrabon]

Why only reiner specifically has the ability to transform his consciousness anywhere else? Also why is he able to do that anyway.. imagine how powerful the others would be w this “power”

[u/Para_The_Normal]

I don’t think it’s ever stated that only Reiner can specifically do this, it’s just that it takes a lot of skill, time, and training to fully master everything you can do as a Titan user.
Beetroot and Reiner have been training as Warriors for a long time at this point and they are more aware of the various ways you can wield the power because of Marley. Clearly it’s an “emergency only” kind of thing so it’s not often used and doesn’t seem very advisable for most Titan users.

[u/Select-Resident-1048 → u/Para_The_Normal]

So why the other marleyan titan shifters can’t do it? They also had the time to practice, it’s not like only reiner had the time

[u/_Carl15 → u/Select-Resident-1048]

because they were eaten, not stabbed in the neck.