"also feel free to elaborate where I "made a couple of leaps," if I missed something important in my (cursory) investigation I would like to know."
It's not that you "missed something", it's more that you made some assumptions which could only be verified by manual checking, as you've realized.
Are they reasonable assumptions . . . probably. I'm using "leap" to mean "assumption". Had I said "outrageous leaps", maybe that would have been out of the realm of assumptions. But they are assumptions nonetheless. My main concern is that some certain individuals will take your assumptions as "gospel" and downrate with no further due diligence.
Are your assumptions red flags? Yes, and they indicate the need for scrutiny.
Now, let me specify what I saw as assumptions.
"Clicking the link verified my first suspicion that it is a phish, but the URL raises the prospect that it was a good site compromised to host the scam."
You used the word "suspicion", which as far as I understand it means it's an assumption. You also said "raises the prospect", which again indicates an assumption.
At this point I'll repeat: Were they reasonable assumptions? Probably. Are they red flags that call for further scrutiny? Definitely.
Will they prompt some individuals to rate based only on those assumptions? Unfortunately, they probably will.
"Further investigation suggests"
Another assumption. Reasonable? Probably, but an assumption nevertheless.
And there's definitely a "cause and effect" assumption (and these can be shaky) between your 4. and 5. items.
Plus you said that you marked the site green, and it seems you did so based on these assumptions alone. It may very well be safe, and for the reasons that you assumed, but since you've probably achieved some regard as a rater, others may be tempted to follow your lead, and their ratings would likely be based on those same assumptions ONLY.
Had you not made the comment about rating, I probably wouldn't be any more concerned about an assumption that leads to more scrutiny . . . which I'm never concerned about at all, and I think it's good to show that there's good cause for "suspicion". But the fact that you mentioned you rated, and implied that rating was connected to the assumptions, is what concerns me about those "leaps" (especially the one between 4 and 5).