I agree, in all my training, there was very little time spent at speed. Only once in the practise session for my Mod 2 did I get up to 70 and that was on a quiet dual carriage way. For my test I didn't have cause or opportunity to go above 50 due to either speed limits or traffic. Lots of time spent at 20mph - due to that being the speed limit around most of the roads in Oxford!
I heard this a lot when I took people out for post test training, and from picking up students who failed with other schools.
Unfortunately it's a business, and some training schools focus on the instructor's customer service experience and not on the quality and content of the training.
One of the (many) things that spurred me setting up on my own was being dragged over the coals for doing 'too many miles' and using too much fuel: having maximum mileages imposed on me. Also being encouraged to waste time off the bike - effectively ripping the customers off.
I fired a couple of instructors who insisted on following this method, and who consistently didn't hit minimum target mileages that I'd set. For an instructor to cover every topic effectively you need bum on seat time - that seat needs to be attached to a motorbike, and you need to be holding the bars.
I worked for a couple of schools who wanted the candidates to have a good time but the teaching element wasn't that important. Many people confuse a good instructor with someone who was nice to them: get lucky at test and think the person that trained them is a genius. When it couldn't be further from the truth.
As an examiner you get to know who does the job properly and who doesn't. We had a saying as examiners, and it was told to me when I was starting out as an instructor: 'You can tell whether or not they are likely to pass by who's brought them up for test': because we knew who would do a good job and who wouldn't.
I cannot tell you how many times I've had to grit my teeth through a test debrief because the smarmy creep of an instructor, who, for whatever reason, brought a totally unprepared beginner to test and led them to believe they were ready, just to take their money. They can then hit them again in two weeks for a retest fee. On occasion, as I'm walking into the car park at the beginning of the test, pulling me to one side asking me to make sure I brought the bike back because it was needed for another test later on! And no, you are not allowed to say anything.
Unfortunately the customers don't know what goes on 'behind the scenes' as it were. Many think all training schools are the same: I've seen both sides and they are not, but unless you are a conscientious professional you would never know.