I used to remember being confused at to whether or not Ash was getting old during the series, as in some episodes he'd be this tiny midget that was almost a foot smaller than misty, other times he'd almost be Brock's height.
I think the whole thing where women often were crazily tall was that the anime wanted to avoid portraying women as a weaker sex, as many (before you bite my head note that I didn't say all) anime movies/shows portray women as being extremely reliant on males. Since most people associate height with power, making women tall would instill the thought that they were powerful opponents not to be underestimated.