I agree with the extension, and how it's not the most ideal. However, I disagree with your interpretation of the keyword.
Amplitude: The amplitude of a periodic variable is a measure of its change over a single period. There are various definitions of amplitude, which are all functions of the magnitude of the difference between the variable's extreme values. <--- From Wiki
Yes, this concept could be considered abstract but then things like, VR, religion, google, etc, and any other form of measurement, by that logic, would be abstract concepts too. Does that make them lose search value? I don't think so... but maybe. Also, amplitude has multiple definitions - that's just one.
When I first got it, I thought it would be a cool brand for something to do with music (amps) - but the possibilities are far beyond just that. Also, the .info extension is on the rise. There are many websites of high value that use it. For example, my personal favorites: dogechain.info and blockchain.info - very reputable and frequently visited by millions a month.
I do appreciate the feedback though, even if I don't agree.
Various perspectives welcomed!