His biggest mistake is in assuming that because he can't see the sun to check if the site is aligned with the sun on august the 13th(haha) because of a ridge he thinks that the olmecs wouldn't be able to align it either
thats cos he's a geographer and not an astronomer.
Theres more than one star in the sky
and they can't be seen in the daytime
theres an oft repeated error that mesoamerican temples are aligned to venus because they all open towards the east.
like the sun has nothing to do with it right.
we all hate that don't we
first rays of the morning sun coming through the window.
doh

its very easy to see that this guy has no idea what appears in the heavens on a nightly basis from his line "so unless some sort of 'relay station' existed on the adjacent hilltop, neither of these key dates could have been calibrated by naked eye astronomy from Teopantecuanitlán."
he never even visited the site at night so how the hell would he know