Being a fired employee, you have to take everything he said with a grain of salt. I wouldn’t however be surprised if QA has been reduced in Apple, going over my experience of iOS/macOS over the years. It’s not a rare occurrence in the industry as a whole as fast feature releases make money, while good QA doesn’t except in the long term (brand loyalty/reliability of software). You could say Apple have short term priorities, which kind of makes sense as the CEO has shareholders to please.
If there weren't a number of other people saying the same thing, your assertion would be stronger. But there are. Whether the person was fired or not is irrelevant to the accuracy of what they are saying. The quantity of other evidence that supports what he or she said supports the credibility of what they said.