Nick, yes I believe it returns to the pre hover figure once the helo is in the hover as does the RCDI, which shows that as you are raising the lever you are increasing the pressure under the disc - surely you cannot argue with that.
Our sticking point is that you say once established in the hover, the pressure distribution is the same in an IGE hover as it is in an OGE hover - and I agree!!!
But I think that you are allowed a lower lever position and less power in the IGE hover because if you did not the helo would climb because the proximity of the ground had caused an increase of pressure under the disc.
The proximity of the ground produces 'excess lift' for want of a better term and you dump the 'excess lift by lowering the lever. Having lowered the lever you are no longer producing 'excess lift' only the 'exact lift' required to hover. In the steady state IGE hover I agree that there is not a cushion of high pressure air under the disc but in coming to the hover or lifting to the hover, the high pressure under the disc would make you climb if you did not reduce your IF by lowering the lever.
To sum up - Cause of GE = increase of pressure under the disc making the blades more efficient by appearing bigger to the air- Effect - lower lever position to hover and less power required.