In this instance, a system used by the cybersecurity team to do its actual job was breached - not some development or testing server.
We don't know what it was exactly that these attackers were looking for or what they found. But it is absolutely possible that the information they gained enables them to protect an ongoing or future attack against Microsoft's customers.
It doesn’t matter to customers if Microsoft teams is down and we are talking to each other internally using iMessage and signal but anything that is in the data path is production.
I’m going to take a wild guess here and say you don’t really run any kind of system. “Internal is not production” is the weirdest statement I have heard in a long time.
Of course these systems are production. Not only production, but _P1_ level production.