I should be clear I'm not some upload philistine. I agree with you that Openreach should be selling much higher upload on FTTP.
They have no technical reason at all whether selling GPON or XGSPON for the tiers they offer. Probably still on the Wayback Machine or some other archive.
I railed against Virgin Media when they were offering 26:1 at best and wrote a bunch of articles explaining why it wasn't necessary and they could do better.
Depending where you are in the country hopefully an altnet or Nexfibre / VMO2 will appear. VMO2 are starting to show some signs of at least considering symmetrical on the XGSPON now. It was a while ago mooted as a paid-for extra. We'll see.
VMO2 go symmetrical the pressure will increase on Openreach from their customers to increase their offering: remember that you aren't one of those customers.
This would likely initially take the form of an upload increase the CPs may pay for on top of existing tiers much as it did with FTTC.