I don't really understand all the scheme stuff, but while looking at Archiving I noticed that various compiler settings were different between the QL and MDI targets. Can they be shared somehow? Seems daft to edit them twice.
The QL Info.plist seems not to include a min OS version; the MDL one does (and it might be wrong).
I'm not sure - I think the point of schemes was to separate these things out.
The structures of the info.plists files are the defaults as created by Xcode - I just created a couple of test targets, and indeed only the Spotlight importer had a 'Minimum system version' by default. I have no idea if this is a quirk of my install or something considered on Apples part though.