This is 100% true.
If your rub contains a bit of salt, even 12 hours can give you the briney (sometimes called "hammy") taste to the ribs.
Ruined quite a few racks before learning this lesson.
Now, I only rub about a half hour before, while the pit is warming up.
Ribs only have, as the thickest part, 1" from top to bottom. You don't need hours like a pork butt or brisket for your rub to do the work.
To the specific question of 48 hours, I would say this is just too long, even with little to no salt. Again, from my early disasters, too early will "leech out" a ton of moisture from the ribs, which is then a double whammy: dry and hammy.
Just my .02, so YMMV