WS-X4712-SFP+E module can't put into an R-E chassis ?

Does anyone know why is not possible to put a WS-X4712-SFP+E - module into an R-E chassis?

The module has the same connection to backplane as the WS-X4748-UPOE+E

and this one works in a R-E chassis.

I know the restriction of Cisco that the 4712 is only supported in 4503-E, 4506-E,

4507+E and 4510+E, WS-X4448-GB-SFP, but why?

Are there hardware-restrictions, is the backplane different?

The solution:

The reason is the chassis itself.

The 4712 has a 48 gigabits per-slot capacity. You need the Sup 7E on the R+E chassis to achieve the 48Gbps per slot in order to get a 2.5:1 over-suscription rate.

On the R-E chassis, the 7E defaults to 24Gbps per slot, and the over-subscription ratio increases to 5:1 which was considered unacceptable. Hence we have disabled the working of the 4712 on R-E chassis. It is a chassis limitation.