Thanks for the inquiry.
For more information about that channel's features and functionality, you'll want to contact the channel provider support directly to inquire further. Many channels on Roku are developed and maintained by the channel provider themselves.
Thanks,
Danny
In case anyone is wondering, whatever it is that was done, either by Google or by Roku, it did change the sign-in behavior, but it didn't fix the history. I went back the the work-around, which actually (still) does work, albeit with the noted limitations.
Unfortunately, it's still a mess. Logging in with brand accounts ONLY is the only thing that works for me.