Yeah I know that. I mean, I've scanlated it.
It certainly feels like a prequel because we have a proper introduction of the MC and the nurse and we also learn that Yukino has never been in her office before. But in Hokenshitsu Sensei to Mōsōsuki-chan (I should have translated the title!) it doesn't quite seem they have the kind of relationship they formed at the end of The Delusional Girl and The Wicked Nurse. I wouldn't call it a sequel for the same reasons stated above.
Now, morino seems very fond of these characters since she has drawn a sort of early draft in 2018 and then two oneshots in 2019 with both Yukino and Kurosawa as protagonists, and it's a shame we don't have a serialized manga with these two, but it seems to me they are different stories with no chronological connection. Unfortunately they were published on two different magazines (one yuri and one seinen), with two differents lenghts, with little to no chance of being able to continue the story on either magazines.
I hope morino will make a comeback one day, I want to see more of these two.