This isn't the first time the intel MEI has been updated in the UEFI. People have been flashing back and forth UEFI versions with older and newer intel MEI versions without even realising it for some time. The only reason you are now being told not to flash to a older UEFI is for the people who plan to use a IB CPU as flashing to a UEFI with a older MEI version in systems with a IB CPU will surely result in a system that won't POST because it won't recognise the CPU.