I had my son in law listen to these recordings including one from 3500 kHz LSB.
He is Mohawk and speaks some of this aboriginal language.
He has positively identified these as being "native". He describes the transmissions as "short answers" and "responses". He recognised a few words, definitely words like "STOP" and "REPEAT".
He was not sure of the dialect, maybe Mohawk, maybe not, wasn't sure.
Pesky "Wind Talkers" perhaps?
cheers, Graham near Ottawa Canada