I noticed the other week, that the WWs I googled were all 6'1-6'3. Dunno if that's new or if the distribution is the same as 10-20 years ago. Garry, Leon, Shavkat, Morales, Prates, Malott - all tall. JDM, Burns, Neal, Brady, Usman are below or just 6'0 though.
GSP was 5'10, Hendricks 5'9, Koschek 5'10, Lawler 5'11, Daley 5'9, Alves 5'10. Kampmann 6'0, Hardy 6'0, Fitch 6'0. Condit and Diaz were taller, like 6'1-6'2.
Height does matter when choosing a weight class, ofc. As does frame. Max is tall, but a smaller frame. Same for Sandhagen. Along with other things, like preferred/developed style of fighting and ease of diet (see GSP struggling to eat enough for MW).
It could be that weight cutting has improved so guys are able to be a little bigger.