I remember a conversation with a GSA (RAF gliding) instructor with 1000s of hours who told me that the British Gliding Association would not accept his experience because it wasn't up to their standards!
I once took a painful 14 hours to convert an RAF motorglider instructor who claimed 1000+hrs, and had a PPL, onto a simple (fixed gear, fixed prop) SEP, signed him off rather against my best judgment, and 10hrs later he bent the aeroplane failing to show adequate judgment and was banned from flying it again. I apologised to the aircraft owners profusely afterwards as I should have listened to my inner voices and never signed him off at-all. Standards vary a lot, and sometimes have to be absolute.
G