It's not enabled on phones. He had to force enable it on his phone. Can't do that on Pixels. So we have to wait for Sprint to push the network config update to devices to tell them they can use it. Sent from my Pixel 4 XL using Tapatalk
Apparently the Pixel 4 is capable of B25 + 2xCA B41 (3xCA total), no B26 + 1x B41, and 2xCA upload B41. So whenever Sprint enables it, it should work.
(Edited with correct CA combos)