Yamaha is by no means unique in this respect. to the best of my knowledge virtually ALL arranger keyboards suffer from this reverb disease and it was the key to the success of my Resources for the PA arranger series. Of course I did a lot more than tweaking the reverbs but ootb it was always the first thing that I did to Registrations, Performances, User Progams or whatever name you fancy giving them. Unfortunately in choosing another style the arranger nearly always defaults to reverb settings of approx. 64, at least on my Korg PA800 and on many,many more arrangers. Another thing why I do not set great store by Songfinders or whatever they are called.
Finishing a product some guy at the factory just sorted out four right hand sounds ( default settings) combined them wit h style (default), adjust the tempo and pronto: another song arrangement was born. Reverb is like a good "tiramisu ". Gorgeous when eaten in the right proportions ! On drums I rarely exceed a value of 15-20, on bass I generally opt for no reverb at all, whereas I tend to drown my strings and pads in them. Amazing it took them nearly 20 years to get down to this kind of basic knowledge, truly amazing.

regards,
John