All sorts of 'interesting' set ups on the Baja Divide route if you go searching around online a bit. I rode the southern third and the cape loop last winter on a rigid 29er (
http://www.bikepacking.net/forum/bikepacking/post-up-your-rigs/200/ ) Post 207. I think a rigid fork with a puffy tire is plenty and I normally run a fox 140mm fork.
While most front suspension forks don't/won't suffer sudden failure it does happen on occasion. That's something I wouldn't want to have deal with in the Baja where remedying it could be a bit of an issue with limited bike shops, but each their own.
Rigid forks for certain routes make sense, but as with anything people ride whatever they prefer, have access to, etc...
I'm heading back down there on Sunday to ride a different section for a few weeks and will have my bike set up pretty much identically as last year.