Welcome man,
I'm of the opinion that destructable environments are destructable environments regardless of your system. If HL2 does have destructable envirnoments that affects gameplay then no matter what the system, it'll load it, very slowly if need be.
I doubt Valve would make it so if you're rnning on a low spec system that things won't load up such as destructable environments. However, in UT2k3-4 you can adjust the physics detail in the game, so maybe something like that might happen in HL2. Like I don't think you'd be able to change the ability to turn off and on deformable terrain for example. I'm probably wrong.