IMO you would be better off posting this in the main 3-rail forum, MTH isn't going to answer here.
Pittman (now owned by Ametek) is one of the few companies that makes a 7-pole motor, so I would guess that's what they're still using in the premium locos large enough to accommodate it. For sure they are not spending the money on Buehler motors. I think the label on the motor actually says Ametek, so their lawyers probably advised them to stop printing Pittman on the box.
To my knowledge, smaller Premier locos like the 0-6-0 and 0-4-0 switchers never used Pittman motors, instead making do with the ubiquitous 5-pole Mabuchi RS-385.
Honestly I'm not sure how relevant it is anymore. I've done a LOT of first-hand testing. I've observed that operation is more affected by the gear ratio, whether or not the gears are back-drivable, and the electronic speed control algorithms than it is by the quality of the motor. The motor and the speed control algorithm have to be well-matched. My $.02.
