That's very interesting. My college room mate is that height, and he has the same sitting height as me, or maybe 1 or 2CM more. Meanwhile, my father is also 188CM and has a sitting height between 98-100CM. I really like to hope that I can pull off 188CM, which is my dream height. Your data doesn't lie, but it seems to me like most 188CM guys I've sat down with (and they're fairly common in the 20-30 age group) do have SH higher than 96CM. My wingspan is 185CM 6'1, and I hope that won't prove to be a limiting factor. When I wear stacked lifts to be 188CM, I do notice that my hands are higher than those of other 188CM guys when we're in pictures together. But, the right clothes can mask proportions quite well.
Also, my tibia to femur ratio is already ideal at 0.8. I don't want to lengthen more than one segment, but fear that adding more than 7CM to one segment (my goal is 8CM), will make me visibly disproportionate. I guess that I'll only know for sure once I'm lengthening, but I will still take a slow and cautious approach and do lots of research beforehand, just to be sure I have a good idea of what to expect before permanently altering my body in such a significant way.