The vehicles clearly are not the standard armor package one would get off the shelf.
If we look at the 3rd edition 3mm Boron/carbon filament plate is an AC of 35.
I'm guessing without the original designers saying it directly, TMP might have redone the armor on the vehicles, or added add-on plates to up the armor, but that doesn't take into account the weights of the vehicles presented are standard weights.
If we look at the Ranger it has an AC of 100. The armor on the Ranger was only rated for 7.62 AP at the maximum, so we have something here that doesn't add up either.
Add-on armor or reformulated armor plates might be the answer to this question.
This link provides the information required to calculate the weight of add-on armor for boron carbide
https://www.eticeramics.com/products...etproof-plate/