Update: Couldn't figure it out. Activated eSim, deleted eSim, rinse and repeat a half dozen times. And then I was locked out of eSim activations for 24 hours. Thought I'd try to request a QR code sent through postal mail, which I mentioned above, and the order was 'on hold' until I accepted AT&T's T&C (Terms and Conditions), by inputting phone number and billing zip code. Both of which did not work, gave an error message. Soooo chatted with AT&T once again, this time it was around 7:20PM. They couldn't figure it out, trying to tell me to go to menus that aren't even there on the iPad/iOS side.
My last ditch effort was to go to an AT&T store. Friday nights, most closed at 7PM, but found one that closed at 8:00PM. The time was now 7:30, and I zipped out of the house and got there close to 7:38, there were several customers already being helped by the one guy there. Didn't get assisted with until 8:05pm and I explained the situation.
He didn't know exactly why it happened (but probably a provision error where it was thinking that specific Line 3 was still with an older iPad Data device (the 5GE/LTE as highest capacity), but when he added a new iPad Data line (Line 4), it detected the 5G/5G+ signals right away. So I went that route, mentioned to cancel the third line in 48 hours so that is what I will do.
But so far, everything is working good. Hopefully this is the end of the eSIM nonsense, as all my devices are all eSIM activated now.