I don't imagine that surfaces are going to have saving throws, unless they are generated by very specific spells. They don't have a DC assigned to them so there's no saving throw to use. Individually giving every surface in the game a DC for a saving throw might not really be worth the effort, and might cause a great many things to bug out.
(And let's be real, if saving throws for most surfaces were possible, most enemies would coincidentally succeed the vast majority of the time.)
No, surfaces already had saving throws even before the patch, other than fire. They don't show the roll though and only half the time would the little dice icon pop up over your head. I tested out running across different surfaces multiple times. As for the update, OP is right. Now when you run across a large swathe of flame, you only take damage the one time.
Edit: Oh and acid didn't have a saving throw, but it doesn't persist after you leave the surface. You only get the -2 AC penalty while standing in. Run over it and you'll be fine
At first, it didn't seem right to me that running over 10 meters of fire posed the same danger as just touching the surface. Now I think, once you've caught on fire, you can't get any more on fire. So it fits immersion and balance pretty well.