That Tumblr post is interesting, though I don't really agree with the conclusion it's reaching. I personally never agreed that Aerith was only attracted to the "Zack-like" parts of Cloud anyway, though I could see how those interpretations came up. The OG wasn't very clear in what was Cloud and what was attributed to Zack/Jenova/other scrambled memories.
No matter, Aerith knows Cloud and Zack are two different people, even if they share similar attributes. In that eyes moment I don't really buy that Aerith is thinking, "Oh this guy is different from Zack." I think she's thinking about Zack. Period.
Cloud says all SOLDIERs have Mako-colored eyes and Aerith gets bummed out because she's reminded of Zack's eyes once again. She says, "yeah, I know," with such sadness. Then she gets down from the slide and says she has to look forward, not back. But that sentence is again said with such sadness. Aerith is desperately trying to move forward, but she can't help thinking about Zack.
I know the Tumblr post is arguing that Aerith's then continued feelings for Cloud means she likes Cloud for Cloud and not for Zack, but my disagreement there is just that I don't really see this Aerith (Remake!Aerith who knows things about the future) interested in Cloud like that, yet. That'll probably change in the next installment, though.
But then Zack shows up at the end, which could then upend a bunch of other things. I simply can't see SE bringing Zack into the story (in whatever capacity) and then not having his arc tie-in with Aerith's in any way. If anything, this just means Aerith is even less likely to move on from Zack at this point, if she senses he's alive somewhere.