Little end bushes have been honed forever without a problem. I bet they are honed rather than reamed at the factory.
You would be wrong. In a production line setting a hone requires more skill to use than a fixed sized reamer in a mill (or at least a pedestal drill with a big quill) as the workers are usually paid as little as possible the reamer wins.
You can't ream a porous bronze bush, it blocks the pores, but you can hone them.
That would be Phosphor-bronze and you definitely cannot hone them for the very reason you state - the hone lays the grain/pores over and blocks them - they are universally drilled and reamed.
I've always bottle brush honed nickasil and alloy bores, and are recommended for the job.
Actually if you read the product notes on Mahle's website (the people who made Galnickal/Nickasil affordable in a mass production setting) they specifically recommend against honing such bores unless you are using a special and very, very hard hone. The reason is in two parts and quite simple - Nickasil/Galnickal is bloody hard itself and much, much harder than old style hones, particularly readily available bottle brush type hones - those sorts of hones either wear very quickly and clog the Galnickal/Nickasil (the very reason why hot soapy water and scotchbrite is recommended for servicing and acid for severe alloy (from pistons) clogging).
The secondary reason traditional hones are specifically not recommended is that as the hone sacrifices itself whilst doing nothing helpful it creates local high temperature spots which can cause the Nickasil/Galnickal coating to de-bond from the alloy cylinder, with obvious fatal results to the cylinder.
If you have got away with using bottle-brush hones on carbide bores I can only suggest that the inevitable disaster is overdue.
As a brand Sunnen made/make excellent honing machines and I am sure that suitable hones are available for those machines.
BUT
The carbide coating on OEM cylinders tends to be very thin and it is quite unlikely that an otherwise unserviceable barrel will be recovered by trying to hone out imperfections or re-introducing hatching - this is not true of all OEM cylinders (Ducati being a good example) and is generally not true of cylinders processed by aftermarket carbide coaters - but it is universally true for OEM BMW cylinders.
