There are other reasons that the women could be there. I am assuming they were buried identifiably as soldiers. It seems that large armies right up into the 19th century tended to include a few women passing as men. There are some famous owoman warriors from our own Revolution, a couple of whom had been along with their husbands and started helping with the cannons and such, and a couple who were not found out until killed or after the war was over. Amazons! is just the attention getter for the writer. There is NO confirmed set of women warriors from any time anywhere. Long ago such a culture could only include a tiny fraction of the women in a tribe because women's time was necessarily taken up with pregnancy and birth else the tribe would die out quickly. A woman had to have many children for 2 or 3 to attain adulthood. If you postulate a tribe with modern antibiotics then Amazons as a culture might be possible.
the song "When I Was A Fair Maid" comes to mind...
"when I was a fair maid, about seventeen,
I listed in the navy for to serve the Queen,
I listed in the navy, a sailor lad to stand,
for to hear the cannons rattlin' and the music so grand..."