Crab,
You said "yes it does" about the altimeter, but gave no numbers. For an S-76, there is an altitude drop when lifting, then it returns to the proper altitude when stable in an IGE hover. What does yours read when in the hover?
Vortecy,
the issue is that pressure must return to the baseline (same as OGE) when the lever is reduced to hold the hover. While in the hover IGE, the pressure is the same below the helicopter as when in an OGE hover. The ground does not raise the pressure under the helicopter, the pitch lever does! The ground allows you to use less pitch.
Guys, we are now again going around and around. Try to think of this this way:
If the pressure is greater below the helicopter in a certain circumstance, how does it act on the helicopter? How would it be measured?
You must break out of the old words and physical models that your instructors taught you if you are to fully understand the concept of Ground Effect. The ground supresses the tip losses, and makes the blades/wing behave as if they were much longer, so they need less angle of attack. This means less tip loss, and less induced drag/power. Pressure does not build up between the aircraft and the ground, there is no "cushion"
If you cannot understand this, that is too bad, but that does not make pressure build up!