>>677199She only debuted as Uto last December 14 and Shion's last APEX stream last year was October 17.
Uto could be referencing that they got to play with each other even before she was Uto or they did manage to play APEX with each other around December 14 ~ 31.
Also, Shion never have once told her chat that she played APEX before with a friend off-stream. Also, I noticed that she claimed that Shion messaged her that they should play again. That alone makes it seems that they're close or already friends since she claimed it's Shion sending a message to her and not Uto to Shion.
You see, Shion is very open about things like this, she will often namedrop people who she messages or interacts with especially if the other party is a vtuber and things that she did off-stream to her chat but I never once heard about a story like that from Shion.