RE: "It's unclear why Apple is selling the iPhone SE again,"
NO, it's NOT !
Cook & his entire team are fighting for their jobs !
Cook OVER-played AAPL's hand when they moved the iPhone product line so Upscale ... now, they are trying to correct that Mistake as best as possible.
Cook can blame it on China, but name another company on this planet that has moved their product line so Upscale (in such a short timer period), & been successful ... I'm UN-aware of any.
A 5" version of the 7+/8+, with an A12 & 4 GB of DRAM & priced right, say $649 USD, would correct the Ship.
Unless / Until that happens, AAPL is Doomed under Cook !
Hardware Home Button + Touch ID is a FAR superior feature set than FaceID ! ... and considering FaceID is much more expensive to implement, it should have been a NO brainier for Cook to continue to offer updated 7+/8+-like iPhones with "value" pricing.
The fact that AAPL is now offering new SE units starting @ $249 says ALOT about the State of the R&D Pipeline @ AAPL.
Why was there NO contingency plan for this year's models Failing ???
That's simple ... because Cook believed his own Hype !
The UP-sell strategy worked for one year, & one year ONLY, the SUPER-Hyped 10-year anniversary model.
BTW, a buddy of mine was able to get one of the new iPhone X units that we're offered by the carriers here in the States during the extended Thanksgiving weekend ... for, get this, $499 USD ! ... those units went fast, & that deal ONLY lasted for a few days or weeks ... those were the units that AAPL pulled off the shelf on Sept 11th ... actually, it was @ the carriers, when they were ordered too top stop selling them on Sept 11th.
The newly-available SE units "may" experience the same thing ... available ONLY till supplies are gone.
I would guess "NO," though ... Cook & his team are now under ALOT more pressure to produce than around Thanksgiving.
Cook was NEVER the long term answer @ CEO ... the world is now witnessing it.