Also would it include all mandatory options from the factory and all standard items?
It is supposed to include all manufacturer installed equipment, but I don't think it truly reflects all possible options on a particular model. In the past there have been really egregious violations of the spirit of the RVIA stickers - in one known case the manufacturer didn't even include the furniture in the weight. Fortunately (and largely through the safety efforts of Aweigh-We-Go and John Anderson) that sort of abuse has pretty much gone away and certainly the RVIA does not condone it, but they don't do much to actively enforce their mandates either. The RVIA pretty much a gentleman's club and they don't tell tales or slap hands.
Tire and axle manufacturers in particular have heeded the call for proper weighing and I suspect they in turn have pressured RV manufacturers to be more realistic in their weights. But the Rv manufacturers are their customers, so they can't push too hard. The fear of a public spectacle such as the Explorer tire debacle, which was more Ford's fault than the tire company, has probably had an effect.
Bottom line: if the listed gross weight is at or near your limit, there's a good chance the actual weight will be over. Get it weighed before signing any papers or be prepared to spend real money to fix the problem. Maybe including a bigger truck. If the listed unladen weight is anywhere near your limit, then you are in trouble anyway. Nobody underloads an RV, despite their best intentions.