To be fair, "highly likely" was probably a bad choice of wording on my part.
It would make Sana be
the most likely connection to Nozomu, out of all the potential bastard daughters. It's not anywhere near confirmed, as you said, there is no real evidence to that at all, but it's hinting towards that from various directions.
During Sana's most recent visit in the TSS shadow
LEGENDS™ realm, Pegasus basically makes it clear that he wants to inseminate Sana and hints at having done that to Sara in the past. Or at least that's how I would interpret the following sentence.
So I think it's possible that Sara's teacher was being possessed, or at least influenced, by Pegasus, maybe also HOPE, when he impregnated her. Similar to how Sensei often gets possessed or is being taken over by various entities.
To me, it would be a little random if that happened to just be some unnamed teacher. Instead, it would be somewhat logical if it runs in the family and Nozomu was the one involved. After all the teacher was supposed to be a family man.
Now I'm not as versed with the timeline as the lore masters, but I think it would fit his profile. Besides, Nozomu, the god, is basically either HOPE or connected to HOPE, so it would fit from that perspective as well.
Similarly, it seems a little convenient that Rin does not know anything about her biological parents, except that her Mom was crazy and a slut (if I remember correctly?) and her Dad a scumbag. Yumi's Dad basically raped a passed out druggie. And Chika/Chinami's Dad also was not around.
They all have traits in common, and while it would be absolutely possible for them to be just three different bad dudes, it is awfully vague enough to leave the possibility of there being some higher entity involved that coordinated this.
Again, I might be wrong with a lot of what I'm bringing forth, and I'm not as knowledgeable with the gods and the connections and everything, but I feel like there has been a lot of stuff that hints strongly towards this being a real possibility.
Also, it kind of makes me want to replay the game for the first time finally, to just refresh on a lot of things and make it easier to connect the dots. But I feel like it would take forever at this point.