The propose of the distinction of army and navy relates to concern addressed by the first clause mentioned Article 1, Section 8, Clause 12 limiting the duration of their funding.
Which
Which is spesficlyspecifically the prospect of said armies being used to directly take control the country.
Thus the distinction between armiesArmies and Navies is their ability to control land and people more than whatever else they call themselves.
Still, out of respect for the Constitution, Congress should not have referreferred to the air-forceAir Force as something other than a armyan Army. Likewise the marine coreMarine Corps should be regarded as an armyArmy given their ability to operate on and control land.
Its worth noting that this has direct implications on all the other Armies Congress has established ranging from Thethe FBI to park rangersPark Rangers, none of which are enumerated in the U.S. Constitution, and were before the exclusive Provenceprovince of the spesficlyspecifically elected domestic government'sgovernments' of the States.