The standards set for MBTI certification are set by the vending company, in EXACTLY the same way that the standards might be set by Langevin — they get to choose.
The requirements to administer the MBTI are not nearly high enough to qualify anyone to use a psychometric test of any kind, even the MBTI, because they simply don’t require enough psychometric knowledge in general to allow the proper use of the MBTI (sorry, I know this will offend some, but if you are qualified in psychmetrics as a field, you’ll understand). Hence there are a lot of MBTI certified people who shouldn’t be a allowed near ANY psychometric instrument, including the MBTI. MOST (and I stand on this statement) certified MBTI folks simply lack the broad knowledge and depth of knowledge to administer and interpret the results properly.