Sylas was intrigued about Alex's plan originally, not because it was overly clever, but because it required something that fascinated him.
Portal prediction.
According to Alex, Legacy had a database of locations portals would appear in as though they had a pulse on the entire world. Of course, it was impossible for one Bronze tier individual like Alex to have access to the full map at all times. But, because he was assigned to this mission, he gained access to information for nearby regions.
Legacy was truly organized.
Alex, being as thorough as he was, caught all the tidbits of information he could and he found something interesting about this portal in particular.
In the future, or maybe in the past, portals like this one would be known as Winking Portals. They were portals that, for whatever reason, weren't particularly stable and could form, deform, and even move within a certain range.