How so? Unless one posits that every imaginable guitar/amp/effect combo sounds identical (which would make a forum like this pointless) then we have no choice but to assign something in the final musical tone to the gear. And as you point out, there's certainly an aspect of the players persona that comes through regardless. I like to use the word articulation as an umbrella for the player contribution because I don't know a better one, and because for me I've found it's ~80% rooted in my picking hand. Timbre is the quality of a sound, typically you'd think of it as why a given note, say C3, sounds different on a piano than it does on a guitar. The difference is stark enough that there's really no way to fail to distinguish the instruments. It's more subtle, but the same principal can be applied to the various combinations of guitars/amps/effects out there. Each variation in the gear changes the resulting sound's quality (clean, overdriven, modulated, spectrum of overtones, etc.).
If you want to redefine 'tone' to mean exclusively the performance idiosyncrasies that distinguish one player from another, that's certainly your prerogative. I prefer to stick closer to the traditional musical definition of tone which includes both the characteristics of the object(s) that produce the sound as well as how the human player interacts with the object(s) to craft music.