Momoshiki was disappointed with the amount of Chakra Bee's Bijuu possessed however he should have a lot given the fact that he's the 8 Tails.
At the end of the movie Bee was shown still alive which means he probably let them absorb one of his Tails probably.
Throughout the series, Bee and Gyuki have dealt with getting captured and Gyuki being extracted several times.
A Jinchuriki dies if the bijou has fully been extracted.
Bee and Gyuki can be in perfect sync.
Bee can be in control of Gyuki's form and the other way around likely too, seeing as Kurama can speak through Naruto.
Gyuki and Bee have tricks to make sure that Gyuki isnt completely extracted.
Losing a chunk of Gyuki's chakra vs the Otsutsuki's, but having Gyuki remaining in Bee, is enough to not die.
The problem of dying happens when the bijou is completely extracted out of the host.
Naruto could even use the bijou their powers and converse with them, while only having a little bit of most of them.
So its logic that Bee can remain jinchurki of Gyuki if he fooled those Otsutsuki.
Maybe Bee's and Gyuki can make each other their chakra look the same to fool the enemy that the Bijou has been extracted.
Similar to how Kisame and Samehada's chakra were made looking the same.
Against Madara, Gyuki made sure one of his tentacles wasnt absorbed by the Gedo statue.
Those tentacles can regen as they have been cut several times, yet returned, throughout the series.
It was enough to keep Bee alive.
Every bijou has special abilities.
This can be Gyuki his ability.
The ability to use feints and to prevent being completely extracted.
This to keep his host alive if needed and to not die (and ress) from extraction himself.
