Yeah I think this is wholesome in a strange, evil way.
I'm not familiar with the doujins or any raws after this or any word of God statements from hagu, but based just on this, it seems clear that Sasha has genuine affection for Master that she doesn't for others, and other boys in this (senpai 1 and Sanada senpai, at least) just aren't what she wants anymore, since she dodged senpai 1 way back in chapter ~31 to hang out with Master and the whole conceit of the threesome has mostly been about making Master feel some type of way using Sanada-senpai as that means. Alongside other notable things, them constantly hanging out and going to comiket and getting reference materials, and her actually fantasizing about him those chapters ago.
Its all about master.