[thejeff]

Yes. That's how it works.

The spells are cast in the ritual phase. If there are gems in the lab at that point, the order is reissued. Later gem income is added to the lab.
This also explains some of the other weirdnesses. Provinces you took that turn aren't targeted because you hadn't taken them yet in the ritual phase when the new target was determined. More problematically, if you lost a province you lost it after the new site search targets had been picked. Your mage could be casting his spell on a province you don't own.