It's not used that way in American English at all; it almost borders on archaic. Given the purpose of this email was to primarily let their American customers know they'd be raising prices on them, it seems unfair to tell someone they're ignorant when they were sent a message containing verbiage that has entirely different meaning to them.

It is not only correct British english, it would be considered formal and academic.

I understand that American english has diverged somewhat, but I would not have expected this word to give so much anguish. I wasn’t even personally aware that americans used it for a particular terminology.

in the meanwhile, us brits will continue using a literal swear word as our most popular version control system and not complain about it. :)