Tbh, I feel bad for this Reimu, she seems to be a nicehead (from what we saw anyway since why was that little shitbag so shitty, unlike its mother? It's not like she has time to spoil that thing).
Anyway, back to the question: does this really count as stalk_pregnancy, because I think it's not, as, for one, this is not a real stalk, two, she's not giving birth through the normal way, but through the power of belief. She thinks that she's carrying a stalk so she could give birth, similar to this pool #1137.
Several more days later
When I came home from work I found that the flower has fruited a yukkuri.
I really wanted to crush that smug face,
but since it went through a hard time to fruit, I decided to keep on observing.