To my knowledge, many teams (including #469, #60, and #67) have used this type shifting mechanism with great success.
If my memory is correct, teams #469 and #60 both used very wide gears that they slid an idler gear and its shaft axially in order to engage high and low gears.
In 2001, Team #67 used a hex drive shaft and slid the gears on this hex with a motorcycle gearbox style shifting fork.
Anyway, I don't see why folks would argue that this method would be more complex than using so "shifting dogs" to engage gears.
It can be made to work either way.
For those who don't remember, this is the machine that I first recall seeing this type shifter used on (Team 60's 2001 robot):
Joe J.