I'm pretty sure ALL manufacturers will take this stance. I had it when moving from VAG to Ford, both VAG and Ford give you IMI accreditation when reaching Master Tech level (I was Seat & Skoda) and for the AC F-Gas accreditation. and the training must have met IMI standards.
Whether its James Dillon, VW, Ford or Billy Bob Training Centre, if they are IMI accredited then surely a training criteria, standards and subject matter should be at a level standard? (how high the IMI set the bar is unknown to us, nor is how much more individual content training providers put into the course) But it doesn't carry the manufacturer logo or authorisation. Some "generic" MT paths contain subjects not covered by the manufacturer path.
Are the IMI worth anything outside the trade? Another discussion as they are not widely known outside the trade, unlike Gas register etc etc for other trades
On starting Ford they didn't recognise any training i'd taken and I had to start again at apprentice level, I took online tests, then face to face assessments and passed Service Technician, Qualified Technician and Senior Qualified Technician. I had to re-sit the F-Gas as I couldn't provide my cert from VW days and the NLC wouldn't provide a replacement. Upon taking the course and not getting my Ford cert I was told I was already registered with IMI !! (Go figure?......money making for bums on seats). The route to MT for Ford is much harder and longer than VAG from my experience (but Ford is much harder, disjointed, un organised, up in the air, useless too!!)
I suppose, like mentioned already, the manufacturer will always want to train you on their vehicles, their way so as to set a bench mark for training across the network of dealers in that specific country, core competencies, warranty standards, values etc etc
Taking any "non approved" training is entirely at your expense and choice but won't be recognised at manufacturer level. I suppose without sounding harsh it could well be classed as a generic qualification, although we all know the standards would have to of been met to gain the certification standards and that the training standard will be of a much higher level than most if not all manufacturer courses (having done many myself, I don't rate dealer training much)
Incidentally, the training I've done and things I've learned outside of any manufacturer based course have put my in a better position at work to fix / diagnose cars......but has come at a cost I won'r recoup and can really only benefit the employer more
so in a round about way......no training is a waste of money, especially if you took anything from it and is entirely at your expense. But won't be recognised by any manufacturer.