Trying to dissect why it comes across, I think it's just me kneejerking to the 'pattern' of specifically "I am sorry you feel that way". I think my kneejerk disdain of that turn of phrase is correct, though.
Being blunt here: Because that's a terrible apology! You are sorry that I feel this way? We're barely using the same dictionary here; how I feel about a thing is textbook 'stuff you cannot change or barely even fathom', so what is there to be sorry about? You might as well say "I'm sorry for the fact that 2 + 2 is 4". It's not apologetic in any way. It says sorry without taking even a millimeter of responsibility.
A minimal apology that is slightly less condescending might be "I am sorry how our choices led to you feeling this way" because at least now you're sorry about your choices instead of being sorry about how I feel.
I wouldn't want to be buoyed by false hope either, so taking as axiomatic that the moz team wants to hear how to improve matters but are not willing to completely 180º on their sumobot policies, something like: "I apologise for how we've kinda steamrolled y'all with rolling out sumobot. We were trying to improve the state of translations of our knowledge base articles and might have gone too far. We shouldn't have done it without keeping you out of the loop either. Is it possible to have a video call, apologise in person, and try to work out if there's a way sumobot can be helpful for all japanese language users of firefox in a way that works with your excellent work maintaining the KB so far?"
I get that it's just american corpospeak, "hop on a call". But the number of times something that's perfectly normal in dutch culture (a bit brash, but not at all intended to be rude) gets jumped on by americans as being ridiculously rude... well, trying to write a way to be culturally aware of the recipient has to be a two-way street, right?
I dont think this 'apology' is rude, not at all. But it's not apologetic. If you're peeved off at mozilla for foisting sumobot on you, you've already decided to cut ties, and then team mozilla tries to mend the relationship, this is a very poor attempt. In the context of an attempt to mend the relationship this is condescending. Or at least bad diplomacy.
At this point getting on a call is seen as a major chore for a majority of people. It's an already tense situation, trying to defuse it by "hopping on a call" is just not great IMHO. They should at least acknowledge they're putting undue burden on the other side and are asking them to go the distance when they're already volunteering their time.
I'm saying that setting aside the opacity of moving from an public to a private setup.
This is a pointer to a somewhat US related POV, but this is nether a generational thing nor a limited phenomenon: