Currently, all are T-Mobile SIMs. Apparently T-mobile is less popularShockingly, there are some some iPhone SEs still available at the moment:
I purchased a 128GB with Verizon SIM several weeks ago. It looked new and operated perfectly. Manufacture date is 2017-03-08. Interestingly, this is just a few days from 2017-03-06, the date of the SE I received as a replacement for screen repair under AppleCare. My guess: Apple is liquidating their repair replacement stocks.