Having a strong accent can make it much harder to communicate. I don't know if statistically true, but from my experience most of people with bad accents tend to use the language less effectively too. If you're in tech you probably use English everyday if not all the time. With that amount of immersion it's just kind of hard not to be at least mediocre.

Also there's this immense sense of quality about people that speak a foreign language super well.

I think pg meant strong foreign accent combined with usage that just doesn't feel native. Which I feel is strongly correlated.