Yuri doesn't have to be romance, that's what is so great about it.
Hence "wholesome" Yuri.
Yuri is girls' love, is WLW stories. They are definitionally romances, even if that relationship is a subplot, or left ambiguous enough to pass censorship. If by wholsome you mean platonic or non-romantic, then it's not yuri. Still good, let girls be friends - best friends, even. But. That's not yuri.
"Genkai OL-san wa Akuyaku Reijou-sama ni Tsukaetai" is a bit of that.
Reject the shoehorned plot tokens, embrace true "special friends" ship.
I strongly reject the idea that that series doesn't have a romance. That manga not subtle about what it is. The only way that manga has a "special friends" ship is in the 'can't say gay', "they were spinster roommates until their near simultaneous deaths, one of natural causes, the other of heartbreak. They were buried next to one-another so they could be together in the next life as they were in this life. As 'special friends'.", sort of way.
(Note: I use romance in this post as 'a story (or subplot) that covers the (development of) romantic relationship between two or more characters', compared to the "romance" tag on MD, which I suspect refers specifically to M/F romances)