Originally Posted by NatCh
Please note that I have no detailed knowledge of the actual processes involved, so that's mostly guesswork -- considered guesswork, but still guesswork.
But it's a really good guess.
It gets even worse when you go back a step before the publisher/distributor agreements. First, there's the negotiation between the author and the publisher. In simple deals, the author sells, say, First North American print rights to the publisher along with a bundle of ancillary rights like world publishing rights and e-rights. Those ancillary rights are usually transferable, and publishers sell them all the time. Scholastic, for example, bought the US rights to the Harry Potter books. Publishers often buy paperback rights, but sell them down the road to a house that is better equipped to handle them. Insane as it seems, e-rights are also being sold on a regional basis these days. Also, said rights might be sold exclusively or non-exclusively.
Now that authors and their agents are getting more savvy, it's not uncommon with hot properties for an agent to sell all the various rights separately; First North American rights to this publisher, First European rights to that one, etc. Or an author may choose to retain the e-rights and use them for promotion, as long as it doesn't conflict with any non-compete clauses included in the other rights sales.
It can get very messy.