I believe apronin@ made some cryptohome initialization timing changes that could have affected this

Possibly. Can be  issue 822302  (was addressed since).
Looking at this https://uma.googleplex.com/p/chrome/timeline_v2/?sid=140a4810f3242feca19d93788c0a24ce, there was a decrease in time between starting Chrome and showing login prompt at the same time.
But the time from cryptohomed start to the moment it can handle login requests didn't change. Which could cause waiting longer already after login prompt - our  issue 822302 . And related things like  issue 841627 .

If that's our issue, it was addressed in M70. And additional work is pending this & next quarter - a refactoring that should deal with issue 879797.


For other possible causes:
I don't see anything suspicious between 10718.0.0 and 10718.34.0, while the avg time continues to grow over that version range. So, if it's something else on the Chrome OS side, looks like it's more a M68 vs M67 thing, not just a CL around 10718.22.0 (where 68.3440.25 landed) or 10718.34.0 (where 68.3440.40 landed).