Advanced riders can be quite hit and miss, especially the IAM types.
Some are brilliant, others are complete pillocks who are lucky to be alive.
I've personally met more of the bad IAM ones, generally. Most have a number of points on their licences and most are arrogant snobs who look down on everything about you, especially if you don't ride a BMW with all the kit. It seems those who ride the least are the furthest up their own backside, with one guy I know only taking his bike out perhaps thrice a year - Supposedly he does an annual tour of Europe on it, with his mates, yet his odometer suggests otherwise...
Supposedly, there was a time when "you could tell it's an IAM group as at least one of their number has an off, every time they ride out"... This remark coming from a local bike cop!
I met a few who did IAM so they could qualify as BloodRunners for SERV. They were a pretty cool lot!
By contrast, I've heard far fewer bad remarks about ROSPA riders and even less about people who do things like Bikesafe.
Generally, IAM will teach you a lot of useful skills, but you may well get a load of BS with it. It's up to you to take on the useful information and discard what sounds dangerous.
Either way, I hope you have a great day!!