As a native speaker (American) the phrasing is classic condescending soulless corporate customer service speak. 1) You must always apologize, 2) you must never admit fault. "I'm sorry you feel this way about what we did" comes across _to me_ as "what we did was totally fine, it's too bad that you don't understand the wisdom of our actions." That kind of phrasing is also a bit of a trigger because the majority of the time you hear it from companies that don't give a damn how you feel and will fight to avoid doing anything to actually help you.
It's of course impossible to say if this was just an unfortunate choice of phrasing or if it's a sign that Mozilla has become that soulless corporate entity (I say this as a Firefox user for more than 20 years).
It's of course impossible to say if this was just an unfortunate choice of phrasing or if it's a sign that Mozilla has become that soulless corporate entity (I say this as a Firefox user for more than 20 years).