That statement is considerably more than a "theory."
There's certainly more to back it up than there was to the "theory" that PDJT was in league with Russia during the 2016 election campaign, or that he hired prostitutes to relieve themselves on a Moscow hotel bed, both of which tales the MSM ran with without any reservations and certainly without referring to them as "conspiracy theories."
None of the flight logs released so far show him going to the island.