We did not make a technical choice to abandon FreeBSD in favor or something else, we made an organizational choice
to abandon external hosting in favor of owned and operated hosting which required a lot of technical changes, one
of which was switching operating systems.
Yes. Maybe a nice one for the Phoronix website ? I'd guess that OpenBSD would not score that high. OpenBSD is cool for firewalls and servers with focus on security but not sure about speed.
It appears that there's a bunch of benchmarks for various flavours of BSD already there. I'm not sure how to compare these with each other and various Linux distributions in a meaningful way.
White what you say is true, I feel like this has more to do with their engineers being better at or more comfortable with FreeBSD or something like that.