The Americast is a steel tub with a resin backing.
If you want them supported, then you can always lay a few piles of mortar down, and some plastic sheeting over to prevent the two from making contact.
Yes, they can chip.
Plumbers do view them as an upgrade over the standard steel tubs, which also can chip, and don't come with any slope at the back. The Americast has slope at the back.
Anytime you drop a hammer into a tub, it's going to chip. And I've seen handymen pull a toilet, and try to set them in the tub because they are too lazy to carry them to the garage for storage. The quickest way to ruin a tub is to set an awkward 100 pound piece of porcelain with a wide tank into a chip-able surface like a tub. There is no give in either one. You would have to be perfect to set a toilet in without something bad happening.
I'm more inclined to use acyclic, fiberglass and cast iron.
Kohler cast iron tubs are heavy, but they are solid.