Why is "restriping" not visibly indicated in the log?

I am in the process of upgrading a ReadyNAS 2100 from 4 x 1TB to 4 x 2TB. RAIDiator 4.2.23. I am pulling one old drive and replacing it with a new larger drive approximately every other day. After I inserted the 3rd 2TB drive, at some point I received a notification email from the system and my log indicated "Raid sync finished". However when I log into the NAS to double check the status, I notice the Volume icon on the admin page is blinking (green) and hover the mouse over it and it says "Restriping". 10 hours after the "raid sync finished" I got another notification "Newly added drive has more space to expand the volume, will start volume expansion." and 4 minutes later the expansion completed. My concern is that there was no indication in the actual log that this 10 hour "restriping" process was still going on, and I wonder what would have happened if I pulled the 4th drive and replaced it during that period? Complete data loss? I thought "raid sync" and "restriping" were the same thing?