MicroSD allows for a really low cost deployment (availability issues aside), especially when PXE is not suitable.
For the low cost route, boot off USB flash drive.
Good luck doing "deployments" on SD drives and still have it run 6 months later, especially in environmentally unfriendly environments. Theses horrible little things die all the time, even when you buy supposedly high quality ones.
Yeah. The Lichee Pi 4A has one of those under the board, it's really useful.
I wouldn't even blink if they completely jettisoned the MicroSD slot, these have proven to be a giant PITA over the years (slow, unreliable, etc...)
I really don't understand why they would miss that.