Its true. But thats not the problem.
You see, in UDK, when you export a person of 170 unit. he is 170 unit,(true) but you are actually much shorter (defualt setting FPS view). So everything you export to UDK in real world scale become giant scale!
Yes, you can of course change view height, but then you also have to change step distance & speed, & all the default physic, like gavity that have a length component have to be modify. Thats a lot of work.
So many people prefer to stick as close as possible to default character size in UDK, & the default character height scale is about 128 unit, which when convert as 128cm, is a Dwarf or kid.