'Proud of' is an acceptable colloquial substitute here for 'pleased with'.
Really? This must have passed me by
More commonly one is "proud of" one's children or "proud of" one's country - in the latter case especially, your direct hand in whatever "they" did may is probably a statistical rounding error away from zero. Not very different to be "proud of" one's compatriots in the world of technology.
What a strange correction. Nothing they said was unusual or incorrect. It was a perfectly acceptable choice of words.