Don’t Europeans typically work less hours than Americans and do so as a point of pride? I’ve spent over a decade lurking HN, Stack Exchange, later Reddit - and I always seem to see Europeans coming in with the “We work 32 hours at most in my country” or “We have a 35 hour standard here.”

Wouldn’t that necessarily imply a reduction in productivity?

Maybe, but not really, obviously any one individual can have high variance. On a macro level though it's pretty easy to identify trends. The most ambitious European devs will come to America to get the much high salaries. The hiring standards for EU devs are considerably relaxed because of the reduced salary requirements. As a result many of the actively employed EU devs would be in a lesser role than their equally skilled American counterparts which results in the reduced metrics.

It's certainly not something any one individual should take personally.