I'm not sure what Android OS source code you've been reading ... but Android mouse isn't "as in Linux" as far as I can see.
That, or the "as in Linux" bar we are setting is so low that it came from a 1997 Slackware 3.5" installation kit.
Android has most of it's shell made from LINUX kernel and to implement a lot of features, they just take a base of desktop LINUX versions rebrand patch and says it's a brand new feature made by us "google 21.century"
Stratego, the templar who never dies.
Device Information: Windows 10 64bit, R5 3600, GTX1060 6GB, 32GB 3333C16 DDR4 RAM, ASUS DGX soundcard