Change in drawlength between recurve and compound

[The One]

I have heard it said before that the same person shooting recurve will lose about an inch of drawlength when shooting compound. Is this due solely to the more vertical handgrips used on many compounds, or a combination of that and the change in orientation of the release hand?

[Sandy Hancock]

I suspect the D-loop or sling of the release aid may have something to do with it too.
The angles required of the relevant joints to get in line should be the same.