Jabawocky;
jamsquat pretty well hit the nail on the head from my interpretation of the conversation. I didn't post the suggestion to enter into a debate on the why's and whichforsuchly's, but why dont you just do what I did and ring the bloke. He is a rather nice and informative member of a mob who I would not normally resort to for such information. AOPA want it scrapped I understand.
AD-ENG 4 is not part of any schedule of maintenance that I can gather, but is separate to. That is, given certain notation has been made on the MR and oil uptake etc have been monitored.
I would suggest that AD-ENG 4 will not be scrapped, but it may be modified in any rewrite of the regs so that it would be incorporated into the schedule of maintenance, whatever that may be.
In the meantime, it is a valid and useful piece of regulation.