That does appear to be an omission of a "quicker picker" method. I suppose it is all what you are used to. I find that trying to find a number on a list, then type it in, to be also inconvenient. Or looking at the reminder listing printed on the keyboard, that "071-120 = Organ" (on my keyboard, while also remembering that accordions and harmonicas are also listed under organs), then after having typed in 071 and Enter to start at that range of tones, I have to then additionally scroll through them all with the +/- (^/v) keys, then try to decipher the often abbreviated cryptic instrument name.
You could always put your favorite ones into any of the 305 music presets and reference them by a hand-printed list taped to the keyboard. Or if it is constantly connected to computer, you could always select the tones by menu options in Cakewalk's "Patch Browser" (using the WK-6500's Instrument Definition file I've posted elsewhere). When sending one note to the keyboard from Cakewalk, the patch tone-selection will remain until changed again manually or by software (if it is anything like my CTK-5000).
If part of the problem is wanting to get back to the default 001 tone quickly, you press + and - at the same time to instantly set tone 001. (I think I remember that this also works for any option selection, including getting back to song 001 from MIDI files on an SD card. It also resets tempo to the middle default.)
Every method will always be a compromise, when you have so many tones and other options to choose from. The difference between choosing 1 book of 10 on your book-shelf, or walking into the Library of Congress. I guess I would welcome the method that you are "stuck" with.
I also just now noticed (from checking) that the WK-7500 also lacks the numeric input pad. I guess this is a feature that doesn't seem all that important in newer models now that they have the jog-dial with so many presets available to store them in. Perhaps someone should do a speed and convenience test, compare two boards side-by-side. See who selects a non-memorized tone option faster, the old way or the new way.