Well, the afterword (beforeword? I dunno) itself calls this thing "slightly yuri," so I don't think that it'd be too unreasonable to call it slightly yuri.
It was more of the fact that they made it seem that "Slightly Yuri" was a sub-genre of Yuri the same way as "Shojo Yuri", "Josei Yuri", "Seinen Yuri", "Shonen Yuri", and "Subtext Yuri".
That said, I'd at least give this thing props for at least being more yuri than... I don't know, any cliche SOL thing filled with lame subtext.
I'm now scared to ask what "SOL" is.
But yeah, this was an overall solid doujin. Sure, it may not have much but It still succeeds at what it tries to deliver, really strong subtext.