Activation does seem to have turned into a DIY thing if you want access to all options. Tmobile representatives had nothing in their systems showing that the $10/5 months/5GB option was available.
They couldn't even activate or help activate the E-SIM option. On setup, they tried to sell me a $30 SIM until I suggested I would just go to a Tmobile store the next day and probably be given one. Magically, it became a comped SIM. Once it was in the mail, I had an account in their system... and then could set up the E-SIM myself many days before the physical SIM arrived. So that was basically a waste.
These carriers are communications companies. You would think they could better communicate within themselves. ?
So I had half of what I wanted- E-SIM instead of physical SIM but not that $10/5/5 plan. Instead, I had a relatively much-more-expensive-for-much-less-data plan that had me watching my usage more than I had in the past.
This whole move was to see if I could do better than my traditional option from AT&T of $30/3 months/2GB or up to $120/yr for continuous cellular data. I already thought that was a relative bargain vs. many other options here in the U.S.
The plan sold over the phone would have cost ("half price") $60/yr for continuous data but for only 500MB/month which would have been somewhat tight for my general usage. Unlike the AT&T option which didn't care how much of the 2GB was using in any of the 3 months, that was 500MB monthly MAX, so widely varying cell data needs wouldn't work here. If I hit 500MB before end of the monthly period, I would have to buy more. That MIGHT work for me but when one travels, one can easily use more than normal cell data.
This $10/5/5 option works out to only ("less than quarter price") $25/yr for an average of ("twice as much") 1GB/month. But more importantly, if I have to travel and use more than 1GB, I have up to 5GB built into it on those unusual but heavier-use scenarios. I foresee no scenarios where I would ever run out of cell data in this option.
Had I not visited this thread, I'm not sure I could have ever found the way to pick it up. I had actually assumed it was a deprecated or legacy (iPad) only plan no longer available. There is actually much speculation to that effect around the internet... presumably assuming that because it seems so relatively hard to find and Tmobile themselves seem to not be able to see it or have no incentive to push it.
To anyone reading this going forward, I strongly suggest you take your best shot at setup DIY: De best plan options be dere.