To give an example...
2 Marshall Plexi heads with sequential serial numbers coming off the production line 1 after the other often sound very very different.
Then the people buying them will use different guitars, different pickups, pickup heights, strings, signal chains, speaker cabs, and the speakers in them, and play them in very different sounding rooms.
They will both swear blind they are the "classic" plexi sound.
So don't worry about it.
The Alembic "flat" setting is very common. 12 O Clock on most tone controls is not remotely flat. It's just the mid point of the sweep the designer wants to use. Genuinely flat as shown on a 'scope usually sounds like a pile of derrière.