Odd sustain pedal behavior?

Tell me if I'm either imagining things or mistaking what should be happening.

Experiment: Play a mid-range note and while holding the note down, press the sustain pedal and then release it.  Notice the drop in volume of the ringing note?  Now repeatedly press the sustain pedal, let the harp resonance build, then release the pedal.  To me it sounds like the ringing note decays much faster than it otherwise would, like the dampening of the harp resonance is "stealing" a bit of the resonance of the primary note.

It's been so long since I've played on a "good" acoustic piano.. Is this physically accurate?  Is there any way that adding and removing harp resonance can make the primary note decay faster?  I would think that if anything it should make the primary note ring slightly longer.

I've encountered it in a few songs where I have to hold melody notes and pedal out other notes.  It doesn't seem to affect the lower octaves nearly as much as the middle and upper octaves.

Thoughts?

EDIT: For the record, I'm using C3ls, but I hear it some in C3 as well.