That really is unusual. Is it actually useful?
I don't know about the Rexhall that R&H has, but Monacos/Beavers generally come with a superb manual, which covers most anything you wanted to ask, including driving techniques, winterizing, care of the Aqua Hot and other systems and so MUCH more. The one for the 2007 Patriot Thunder I had (a paper copy yet) was at least 18"x12" (bigger I think, but it's with the coach). I do still have an electronic copy, and it's 270 pages long.
The sections are:
Section 1 - General Information.......................3
Section 2 - Driving & Safety..........................15
Section 3 - Exterior & Interior Care..............57
Section 4 - Appliances....................................85
Section 5 - Equipment..................................109
Section 6 - Water Systems............................137
Section 7 - LP-Gas Systems..........................157
Section 8 - Electrical Systems - House .........167
Section 9 - Electrical Systems - Chassis........189
Section 10 - Chassis Information .................209
Index ............................................................261
In addition, the Beaver also included individual manuals for the various systems, including the residential fridge, the VORAD (on board radar), the CAT C-13 engine, and two large accordion folders full of other stuff, from TVs to water filters.
My current Newmar has a (mostly) generic manual but lots of separate manuals for the various systems. Even the Trailmanor 2720SL I had years ago had a (mostly) complete manual plus the individual ones.
So perhaps it's not as unusual as you think, though it's far from universal.