It's not just the "forums", Kodak and Fuji make the same latitude claims about their C-41 films.
This latitude can be used creatively in many ways. This is simply a method of getting proper exposure placement to get a desired result, it is not truly over- or under-exposure.
The biggest advantage for me of re-rating is in this exposure placement, it's like using exposure compensation (the effect is absolutely identical), just a simple way to knowingly "trick" a meter into giving me a camera setting that works for getting a planned result.
The second biggest plus of that latitude is that it makes shooting more reliable with any camera and makes getting reasonable results with a Holga or Diana pretty easy.
Shooting high latitude films makes shooting more fun and reliable for me, I don't need to sweat the back end stuff while I'm shooting and that helps me focus on the moment and make/take better pictures; so much so that for 135 and MF I'll probably be fully switched over to XP2 and BW400CN for B&W by the end of the year.