He's right. The nerds who want WebUSB are leaving or using Chromium on the side. Firefox has just been collecting the nerds who want absolute safety and privacy at the cost of any functionality (which apparently includes removing extensions according to one).

I was floored when I discovered that Firefox rejected Web NFC because they were afraid of it being used on specific outdated Yubikeys. I could understand if they were concerned about it being used to steal credit cards, but the Yubikey scenario is just so out of touch. I can only hope that Web Serial represents a pivot away from that.