If he's anything like me, it's just the muscle memory part. My understanding of JavaScript grew basically alongside the evolution of the Chrome DevTools, so there's quite a lot of subconscious navigation that just feels more intuitively, to me, in Chrome.

It's also a psychological bond to a certain extent, having relied on them during stressful times in my career... before that I had only FireBug and that served a similar purpose but didn't teach me quite as well and did never reach the status of "if the Chrome Devtools are open, I can understand what's going on here"-sense of security & confidence.