It's totally a marathon! Sure, the conditions are lab perfect -- but these are also some of the best runners in the world.
(genuine question) is there only one official body in the world that determines what a "marathon" is?
My understanding is that the Boston Marathon (which certainly seems to be a marathon) isn't considered a "real" marathon because of various reasons (weather, elevation, non-loop nature of the course etc.)
Marathon running isn't necessarily a track and field sport in the way the 100 meter sprint is.
The story takes place after Athenian Hoplites pushes back a Persian army into their ships at the Marathon shores, after which this ship sails to Athens to wreak havoc. Hoplites make the run from Marathon to Athens just in time to defend against Persians and successfully discourage them against further attacks.
After the Battle of Marathon, hoplites who were in the war referred it to as "the run", "we ran", or had "he ran" carved in their tombstones etc. So Marathon became synonymous with running.
Here's the mention of "we ran" in Hansen: https://books.google.com/books?id=lAWEPUkz5sIC&pg=PT164&lpg=...
The story of Pheidippides running from Marathon to Athens (and dying on arrival) is certainly apocryphal, but it's nevertheless the origin of the modern marathon.
"The Persians saw them running to attack and prepared to receive them, thinking the Athenians absolutely crazy, since they saw how few of them there were and that they ran up so fast without either cavalry or archers.
"So the foreigners imagined, but when the Athenians all together fell upon the foreigners they fought in a way worthy of record. These are the first Hellenes whom we know of to use running against the enemy. They are also the first to endure looking at Median dress and men wearing it, for up until then just hearing the name of the Medes caused the Hellenes to panic.
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It's also interesting to note that the Spartan army arrived at Marathon a day late "having marched (140 mi) in only three days."
A single man runs from Marathon to Athens, says only “we are victorious”, and then dies. That’s the legend, but it’s confusing two events. Pheidippides actually ran from Athens to Sparta to request reinforcements. The Marathon to Athens run has the hoplites getting there just in time to see the Persians leave Athens.