I have been taking a good look a the liquid vinyl siding.

Don't be a sucker.

Vinyl paint (that is, paint based on polyvinyl acetate polymer, PVA) is
cheap ordinary paint such as you would buy at any retail store. Adding
fumed silica (very fine sand) makes it thicker, more thick than paint is
usually formulated. There is no value to such thickening other than to
bamboozle the customer.

Basically you are being offered what is (at best) an ordinary paint job for
perhaps twice the going price, with the appearance that you're getting
something better than paint. It's a despicable sham.