I could see it being both. I can't say for certain but I've heard grumblings from wheel holders that the DOT exam has become more picky in the past 10-15 years. Leads to more DQs or limited cards. Which means, more $$$ in retests. Whether the DQs/retests were actually legit or not is for the MEs to know. I wouldn't put it past some corporate/small time MEs to keep the revenue flowing.
The cynical response is that FedEx wanted to save money (fewer physicals, hiring and training costs, and fewer people needed for peak).
Non-DOT drivers are not subject to HOS rules. Despite what anyone may say they can work over 14 a day and over 70 in 8 days. They do not require a 34 hour reset.
Well, part of the cynical response is untrue. Express policy dictates no more than 14 in a day, 11 driving, mirroring DOT. Yes, Yes, Policy can be changed at a whim... but the facts are still there.... it's been policy for... how long? So, that kills off the 'fewer people needed for peak' because everyone is still limited to policy time.