You have obviously never used an XF workstation (Or any other workstation for that matter) as while you are correct in that the PA4x can do a number of the things you mention, it pails into total insignificance compared to what can be done with the XF.
You may not like it but an arranger is a jack of all trades, however it is a master of none, and while it can do things that specialist keyboards and studio equipment can do, it is in such a limited way that it is only of use as a very basic scratch pad. (This Jack of all trades comes from the fact that they were designed for the home hobby player to sound great without the wait, (They derive from the old entertainment organ easy play features) however the bonus of this design is that they are also excellent for OMB, (Something workstation and controller keyboard based systems are not) but you very seldom see them in live bands as most of the features are irrelevant, (Hence the use of specialist equipment in this scenario) likewise in studio production their features fall well short of what’s required, (As also their sounds) hence the reason they are not used in pro bands and studio production)
Personally I cannot see why arranger players have such a problem, (Pro musicians don’t) as they are great for the job that they do, but they can’t do everything. (It’s like driving an SUV and saying it can do heavy off roading or track racing, as it can’t, except in a limited fashion)

Bill