I concur based on the codebase. reviewed it the other day and im left with either.

a) an extension that doesnt match the published code (unlikely)

b) browser sync itself not working the way it claims (unlikely as it would be a major privacy and security violation)

c) what i thought was population of private key wasnt the same (very possible and ill test this theory next time i wipe the laptop)

c is what im going with, and may result from the whole master key set or unset. i think alby prompted or suggested setting and then derives a key from that? which would populate the field but have no way to match existing key derived by other means.