This strikes me as a classic example of being instructed by ATC to do something that you are not necessarily yet cleared to do, and I am sure that at best it will cause a significant increase in level busts, and at worst a catastrophe,
It goes completely against the grain, and appears to be contrary to the wisdom of previous initiatives designed to avoid confusion, for example the "behind the landing XYZ, line up behind." In this example the aditional use of "behind" was added (I presume) to ensure clarity and reduce the chance of any missunderstanding.
Here we have a procedure that may be necessary for ATC operation reasons, and it is clear that all posters agree it is going to lead to confusion. It seems appropriate to me that there would be little difficulty in introduing this initiative if a qualifier is added to the instruction - for example "AFTER ABC, climb FL100.