Anyone know how/why this arose?
Several years ago the CAA formed an IR and IMCr working group on which I sat. They were tasked with looking at the requirements for the IMCr and picked up on the discrepancy that you could do an IMCr in a SEP and then go off an use it ME without any further training or testing. It was decided that we should change the wording so that if you wanted to test in a ME then you had to demonstrate some basic single engine stuff. They also added the requirement for revalidation/renewal. I can't remember if the latter appeared in LASORS before its demise in the end.