Croft specs - too much gain?

[Wegamus]

A typical gain of a power amp may well be between 20 to 30dB, and if its I/P sensitivity is about 0.5V which is typical, that would produce an O/P voltage of approximately 5 to 15 V, 10V across 8 ohms giving an O/P power of about 12W, and 15V about 28W.

That all seems reasonable to me.

I've been pondering the possibility of a feedback loop which had become open cct, and has resulted in a jump in gain.

Why would a power amp have an input sensitivity of 0.5V? Is it because most of the circuits were basically designed before 2.0V digital sources appeared so no one wants to change them? I’ve noticed old Quad amps are 0.5V too, and seen modded ones where it’s been changed to 1.5V presumably for use in a modern setting. My old Nagra power amp had a switch to change it from 1V to 2V which was very handy. I don’t understand the wide variation and the purpose of it when we’re all using the same sources - 2V for digital and a few mV for vinyl. It’s like volume controls too, they’re all 9 o’ clock at best for normal listening when there’s a whole pot to use, just why?