I checked again out of curiosity, and I now have an option to toggle between tiles sizes. I found it under Settings > Home Screen. There are two new options, one for "Continue Watching" to show/hide, and one for "Tile Size" with options for Smaller/Larger.
I am currently using the software version: 12.5.0 build 4176 on a 55" TCL Roku TV.
I received no notification that there was a new option, so it might be worthwhile to check on your own device. Good luck!
DefenderXX they obviously are not rolling it out via an OS update, but one of their background process updates. I have devices on beta builds that are newer than yours (NDA doesn't allow me to mention the build numbers) but there's no such option on my Ultra 4800. You did find it where I would have expected it to be, so that's a positive step in the right direction. Now they just need to roll it out for everyone. No idea what's taking so long.
