Is this new:

MCE upgrade is more expensive booked on AS using AS miles rather than with AA miles on AA for an AA flight.

I booked a couple of short domestic AA flights on AS.com using AS miles over the past 3 months. I have my AA FF# in place through AA. My AA status allows & shows available Preferred and MCE upgrade seats on the seat map. All are more expensive than if I had booked the award using AA miles. One offers MCE for $115. Booked as an AA award the cost is $52. Another is $84 vs $42.

I spoke with an agent by phone who stated both sets of pricing were correct with the difference being my booking with AS miles. I have another similar flight made several months ago where there was no difference.

Is this new?