I also had the same idea when I was waiting for sync of a large file to start (see my comment here).
“Crunching metadata” sounds cool, but does not fit (also not easy to translate). For me the “preparing sync” is better - but whatever the wording will be: most important is that there is a (visible) progress, e.g. counting the meta blocks infos that are transferred as percentage of total meta block information or something like that. Maybe an ETA display would also help.