I have seen bananas used in the hive first hand. as a matter of fact, I helped the guy who swore by it, put them in his hives.
I helped him do it once a year for 3 years and none of those times did the bees get any more aggressive than they normally might, which is to say, as long as we were nice, they were.
he always put the squishy going soft bananas cut into pieces either directly on the frames or on top of inner cover.
I have never put them inside my own hives, but I have put bananas out in a location that were in same condition (well over 100 yards from bee yard) and as they get soft and decay, the sugars and moisture are visible and attract all kinds of insects. If and when the bees find them, they take over and cloud the whole area sucking up the sweet liquid.
He claimed putting the bananas was for a feed source but also generally claimed it kept them bees healthy. Mind you, this was an 70 some year old farm boy who had been doing this most of his life. I couldn't tell you if there is any science about it, but as he told me, "science can only tell you what it is, not why."
anyway, that's about all I can say on the topic.