Last weekend I lost my logbook. Accoring support no chance to restore.
Before I los sometimes some flights at the log.
I was few hours before 100 hours flight. With this loss, some achievements calculations are lost too. Even the data are not lost at statistics an even the reached achievements are not lost.
My polfile say now: 5 hours flight (4:39:04), my stats 427.289 second i.e. 118:41:29, the achievemenst says 50 hours reached, but 5% for 100 hours achievement.
This means some achievements are calculated by log book and others by profile statistic.
My observation:
log - taxi trip
log - pilot program
log - greased
stats - hydoplaning
log - century club
log - night owl
stats - SIDs and STARs
stats - World traveler
log - Jack of all planes
log - Journey man
log - Wing Commander
Due to Microsoft does not support restore of the previous successful stored logbook, achiements in MSFS means your flight statistic combined with logbook stability of MSFS and it´s cloud service 
Hope SU8 brings more stability and standard mechanism to prevent data loss.