Regarding rank grade, it also only assigns the rank grade (on the beatmap on the right side) depending on currently selected game mode. Before I played the same Taiko-specific map, I was under CatchTheBeat mode, and when I scored a SS score, it funnily assigns the ranking grade and only displays when you're selecting CatchTheBeat mode and not any other game modes. (The workaround is to browse Global Ranking while selecting all other game modes, and it'll assign the proper rank grade)

I played a taiko difficulty from CTB mode, and the letter grade was only visible in CTB mode. It was not visible in taiko mode when I switched to that mode. Refreshing easily fixes this so this is low priority.

I just found out that the rank grade letters on the song s at the right side also affects "Rank" grouping. This may cause a bit confusion because it also counts the rank grade of mismatched game mode as well.

I have 575 SS count on osu!Standard, but the filter showed up that I have 576 SS count because one of the SS is coming from Taiko-specific map.