The impact of variable latency is well-known among people who actually study human factors. It makes it hard for your brain to internalize interactions and make them automatic, and it increases the feeling of frustration.

In video games specifically, where I work, it is well-known that you would rather have a game that runs slower, but with a solid frame rate, than a game that has a highly-variable frame rate that is faster on average. (This is more of a continuum situation than a discrete action like a tap, but the basic principle holds).

P.S./edit: Double-tap only means zoom because that is what they happened to implement. It is a convention easily changed. Look at how heavily Apple just revamped their entire interface, for an audience that is arguably much less savvy than the Android audience.

Using double-tap in this way was a mistake; it is an easy mistake to fix if you have enough design vision to know where you are going.