Apple hardware is good, but not priced at the same quality to price ratio because there's no competition. You can get other brands with higher quality at the same price point that better supported by Linux.
I think that was the point there. Not that Apple has bad hardware, but lack of competition and the premium for the product family mean you can get higher specs per dollar with many other manufacturers and you can find hardware that won't require "jailbreaking" or other workarounds or missing drivers to get it working with Linux.
I mean, bugs are a part of all software. Stability is about reliability. That if you boot up your computer you are less likely to spend the first hour or two troubleshooting unless you just did a major upgrade. I'm not saying Arch is unstable, just less stable.