At what point are those punctuality stats taken ?
Cityjet (operated by Scot Airways) are without a doubt top for being ready to depart in my experience, always been spot on. But then ATC slot delays (presumably from down at the London City end) seem to get in the way so actual departure from BHD and moreover actual deplaning time at LCY after being vectored on a Grand Tour of Kent can be disappointing.
The roster for the aircraft is nice and relaxed so any knock-on delays are minimised, or indeed eliminated.