Rob
I hear what you're saying, we had our 9530 as a daily driver for well over a year, I'm not saying they cannot rinse well, I just found you have to be more careful with them than other machines of the era (loading towel loads lightly and being mindful of detergent doses for instance).
When using the more basic 9517 with the single water level because it does a full static fill and will only top up if the water level drops massively, most of the water was soaked up by heavy loads so the water level was not particularly far up the door.
Of course what little we managed to use our 9550 it appears to do a short spin followed by a long spin on the interims, rather than the 2 short bursts of the mechanical dial machines, which I would say is far more effective.
Any machine will do it's job as long as you know how to use it, a 2000's low water usage Bosch will rinse just fine as long as you use it properly!
My point was really that if you want a machine that will specifically rinse clear pretty much no matter how full it's filled or how much/whatever detergent you use a Hotpoint 9506 is probably not going to guarantee that.
I love our Hotpoints and can't wait to get them up north to use them more regularly
Matt