Properties are part of the heap resource, yeah. So if you change a property but not anything in a method or procedure, you may well get away with only exporting the heap resource. On the flip side, the heap resources are still generated from the .SC files, by compiling them!
So say I want to replace a given room's picture, not by changing the picture resources themselves but by changing the room's properties.
(instance demoRoom of Room
(properties
picture 240
; more properties left out
)
(method (init)
; unsullied code
)
)
Let's say I extracted the script resource for this room and put it safely aside.
If I were to edit the .SC file to change that one line to picture 420 and compiled it, one of two things can happen:
If this were an SCI 0.x to SCI 1.0 game, without heap resources, I would extract the script resource again. Comparing this to the one put away, on a binary level should, if I were very lucky, reveal one change: 240 is now 420.
If this were an SCI 1.1 or later game, the script resource would, if I were as lucky, be exactly identical to the old one. Its matching heap however would have that one change.
The luck in this hypothetical situation boils down to small differences in how SCI Companion compiles things compared to Sierra's SC utility. That is all.