The GENOS's keys are wider then on the TYROS, (which I still have) , so I measured them both and found:
An OCTAVE in the TYROS is 160 mm and the GENOS is 183 mm...... or the width of ONE key
That is an odd measurement, are you sure you measured it correctly? There is no defined standard but most white piano keys are 7/8" (22mm), with a 1/16 spacing, so that gives most exactly 6 1/2 (123) octave span. The metric sizes are rounded. Obviously making the key a little smaller would reduce the span and the overall length of the keyboard, so some portable keyboard manufacturers have made keys a little smaller to save space. There are some variations between manufacturers in the key length, the length of the portion extending beyond the black key, and the exact shape of the black keys, but most work with the 7/8 white key.
When you make a key smaller it may be a bit more difficult to hit accurately, but the span between notes reduces which might be easier for some. But the trade off has led most manufacturers to settle on 7/8, although as I said some have tended to go smaller to make a more compact instrument. I haven't come across any which are bigger though.
I don't have a Genos to check. That Yamaha would make it with bigger keys just seems odd to me.
Exact size of key, within reasonable limits, doesn't make too much difference to most average players, but you can imagine that for a very accomplished player who has practiced 10 hours a day for umpteen years, small differences would be very noticeable. That is why so many Classical pianists insist on Steinway. Its not because they are better, ( in fact there are very few experts who consider the Steinway to be the best piano) but because in the most demanding environment you want the comfort of it being the same all the time.
Mike