I think it was since 0.16.2.There was the boost button gone.(Even with holding a carrot on a stick).Befrore the version there was a boost button between 0.16.0 until 0.16.1.
MCPE-20208
Boost button don't appear by riding a pig.
Resolved
Fixed
0
(Unassigned)
53762
Unconfirmed
Phone - Android - Huawei Honor (Specify in description)
Android 7.0 nougat
1.0.4.1
1.1.1.1
Retrieved
But you can still boost by long tapping the screen.