To be fair, this is extremely common, this isn't something Boeing invented yesterday. The whole series of Cessna business jets are on the same type rating. The A330/A340/A350 share a type rating. The 757/767 share a type rating. There are almost certainly more differences between a 757 and a 767 than a 737-800 and a Max.

Not that 90 minutes on a tablet constitutes a reasonable level of training though.