Seems like they have a strong opinion! I suppose I would have to partially agree though - if you have used 4 training providers for 3 courses then something has obviously gone wrong (!) and it might be the fault of the student so I can understand why. However, it is a litte harsh for the guys who decided to do a sneaky multi rating when they were on their holidays and decided to do their CPL and IR at different places.
I do think it is a good idea to do you multi and IR at the same place as you will remain on the same aeroplane and you can do your multi training before your IR and then sit the test just before your IR test, maximising your hours on the aeroplane prior to test. The school I did my IR at was based in the UK so I went to the US instead to get it done quickly
However, I am sure though that they won't expect you to do your PPL, Night, IMC etc. at the same school as well as all your hour building??