We are experiencing something similar. (We have iOS 13.5.1 on our Apple devices.)
With Family Sharing I have an Apple ID created for my child. On my Family Sharing Family Members list, I show up as the "Organizer" and my child is also on the list as [Her Name] Age: ##.
Note: we don't have Screen Time restrictions set up. It's just configured to whatever default is.
My child is logged in with her Apple ID on our iPad. She went to play Roblox but first she was prompted to upgrade the app and couldn't play without upgrading. She was redirected to the App Store on the iPad... she attempted to upgrade Roblox, the iPad prompted her for her password.

But the iPad wasn't accepting the password, it was saying verification failed. I tried a few times, typing very slowly and carefully. Nope, wasn't accepting the password. I tried my password for the heck of it! Nope.
So I attempted to troubleshoot. I tried to download a new app from the app store on the iPad using her Apple ID.... that works fine... it accepts her password, I'm sent an approval request on my device, she completes the download on the iPad. But the Roblox upgrade will not work.
I ran out of time to spend on this so I resorted to my work around ... I signed her out of the iPad... then logged in using my Apple ID... I performed the Roblox upgrade... and then I logged out and logged my child back in with her Apple ID.
Her Roblox app on the iPad is now at version 2.437.406997
Does anyone know what's going on ? Otherwise, hope this workaround helps.