There is a very easy answer to this situation - someone buys rolls, cuts them down, re-packs and re-sells.
This has been happening with Super8 film for years - companies like Pro8mm in california and Wittner in Germany - and that is a much much harder thing to do (think about the fact is has to be re-perforated and spooled into super8 cartridges).
Or, alternatively, has this task performed under contract by Ilford or someone.
Depening on how hard the re-seller wanted to go at it, they could do it themselves whenever an order came in; or they could hedge their bets and contract Ilford or X company to cut down the rolls, on the assumption they could sell the quantity.
A 20", 88 metre roll could deliver, by my calculations, 866 sheets of 8x10" paper - or a whole mix of sizes.
Matt