Bees become quite comfortable and tolerant of their keeper.
If treated gently and not threatened they get along well.
They will even tolerate a jarring event if not common.
The problem with this study is that no effort was made to actually communicate at bee level. They can and do communicate and sticking out proboscis is a Pavlovian response rather than actual communication. Knowing bees can detect explosives should induce study to learn how the massage can be communicated at a higher, more detailed level.