Dana, compensating ports are bores in the housing. I haven't looked at a stock D MC, but many like this: For rear favored bias, both pistons retract, both chambers in the bore fill, when the pedal is pressed, both pistons pass the fill ports (purging ends), then the rear piston passes its compensation port and begins to create pressure 1st, THEN the front piston passes its compensation port and begins to create pressure too...
There are other ways it is done e.g, with a valve (similar to a push-up valve in the bore), as previously mentioned. I haven't seen/noticed one before, but, with the difference in spring strength you pointed out here, I could see how the position of the compensating ports could be equal at rest and the weaker spring causing/ensuring the rear piston passes its compensating port first...Or, just using equally spaced fill ports with a weaker spring (much like a biased ABS MC w/o compensating ports).
But, I don't see the springs affecting the pressure once the pistons have passed all ports, regardless of whichever port setup it has....
Very rough, but might help:
Attachment 57048
Look in the bore. If there are 2 incoming ports only, it is the spring doing it. 3 or more it is compensating port(s)...or a combination.
Interesting stuff!