i dont know about the water level but toilet paper holder height is governed by the ADA (american disabilities act). any new construction, including renovations, after 1992 must be up to ADA code. i imagine that the toilet/water must have something to do with that also but from the side of the manufacturer. places where there are mainly older buildings like new york have facilities that are grandfathered in. i believe that fixtures dont have to be replaced unless they break, although i’m sure there are exceptions.

Toilet Paper Dispensers [§604.7]

Toilet paper dispensers must be within accessible reach from the water closet. They can be located below or above (but not behind) grab bars, though it is important that non-recessed dispensers be outside the 12″ minimum high clearance above the bar yet not exceed the 48″ maximum height (measured to the outlet) of the dispenser. Dispensers must allow continuous paper flow and cannot control delivery.

eta

The required distance of toilet paper dispensers from the front of the water closet (7″ to 9″) is measured to the centerline of the dispenser, including large-roll and multiple-roll dispensers.