Originally Posted by
HNLbasedFlyer
I hadn't realized Avios accrues at the same rate as MP
No, it's even better than that. I use AMEX MR transfers for Avios. MR points are earned at a rate of 5 per dollar when airline tickets are purchased with the Platinum card. So the Avios "accrual" is on top of whatever is earned on the underlying ticket in the program of choice (whether UA or any other).