It's a strange one this because in quiet a few caa and aip's the pilot and ATC internal dept are completely at odds with each other. I have worked with sops written as per UK method and approved by foi. But aip and ATC expect Change at transition. I did ask and was told not to worry about it ATC were run by the military and were clueless.
Even in Europe there are 4 different ways of doing it in aip's. Pilots do not read aip's as a rule.
Personal experience looking at a fleet of 20 aircraft and 60 pilots says there are more alt busts changing at transition. We had a group that were adamant to change at transition and a group that changed when cleared The first group accounted for 95% of the busts. The second did have a couple of busts but they were going to happen what ever the setting was being told to level off with less than 500 ft to go and climbing at 2500ft per minute.