It's true that "linothorax" is not an ancient noun--it's an adjective, which means "wearing linen cuirasses"-- which should be enough to give pause (though yes, it is in the Iliad).. It's also true that the Alexander Mosaic doesn't make clear the material of the cuirass-- but it does seem to be a Roman era copy with a lot of rather good stuff. The padded cuirass worn by Alexander is not a question of when Plutarch wrote, but whether his sources were reliable-- and some of them were. In any case, padded textile or layered textile garments do appear on red figure vases (sometimes with padded strips that look like gambesons. Pic attached.
I am less than convinced by Andrete's reconstructions, and rather agree with a very critical review by Duncan Campbell:
https://www.academia.edu/7536950/Review ... rete_et_alBut the issue will not go away: in the vases, used by Peter Connolly for his reconstruction, you can see that the cuirass is being wrapped around, and has stiff shoulder thingies that stick up in the air, before being bent into place--
https://en.wikipedia.org/wiki/The_Revel ... n_2307.jpgThe Vergina cuirass could be an iron version of the "linen" (whatever it was made of) cuirass, just as the Greeks wore bronze versions of their hats (pilos, but also petasos: shown by N. Sekunda in his rather wonderful Osprey Elite on the ancient Greeks).