They could have tried 1 other version (not 4) and picked either the latest (1.13) or the version that contains the GC improvements (1.12) to test. Usually when you are looking to upgrade something you skim the release notes so testing 1.12 or 1.13 is obvious especially when 1.12 seems to specifically address their performance concern.
If upgrading something avoids a service re-write that is usually the way to go unless you were looking for an excuse to re-write the service in the first place which may have been the case.
edit:
It turns out they did exactly what my comment stated: they tested the latest version (1.10). It's just that this article was published recently but the events happened quite a while back.
Maybe it does, maybe it doesn't. Maybe 1.14 has a performance regression with their specific load and they get screwed.
We'll never know. You know why? They permanently solved their GC problems by eliminating GC.
That's the smart play.
It seems like my comment was just an entry point for you to shit on gc which, ironically, I mostly agree with in this context.
It isn't surprising to me. It's stated elsewhere they tried 4 difference version of Go, up through 1.10 apparently, and had performance problems with all of them. At some point you can't suffer garbage collector nonsense anymore and since they'd already employed Rust on other services they tried it here.
It worked on the first try.
That's not surprising either.
What would be surprising is if any of these "but version such and such is Waaay better and they should just use that" actually panned out. The best case would be that the issue just manifests as some other garbage collector related performance problem. That's the deal you sign up for when you saddle yourself with a garbage collector.