Osmotic pumps tend to be equivalent to a transdermal patch in how the substance spreads through the body, but bypasses the need to go through skin. So, faster initially, but otherwise the dose over time would be the same, assuming the transdermal patch was able to maintain dosage (they aren't, there's a drop-off).

And, just as you said, the entire dose is taken in without any degradation by digestion, or being bound in something.

What I have zero clue about is what difference it would make in terms of numbers. It is equivalent in speed of uptake to subQ or IM injection, which is essentially immediate, just with a slight curve at the very beginning, so tiny it won't be noticeable to someone that experienced all those deliveries.

Vs IV, the initial release is slower with osmotic pumps, but the sustain of the pumps makes everything after that different.

Basically, the pump goes under the skin and leaks the substance into the intracellular fluids, to be taken up by capillaries into the bloodstream.