That might be the reason it works with both apple devices and generic USB charging devices.

It is not just a dummy charger with resistors signalling the charger type but instead has USB host mode chip that can do the standard current sourcing/sinking negotiation.

Pretty neat trick, that.

Since my N9 doesn't charge anymore I can't test but iirc, while the N9 detects and charges using an apple charger, the current is limited to 0.5A instead of the 1A expected from a wall charger.

Unfortunately it is even less than that

According to the standard unauthenticated devices may only draw one unt of current, namely 100ma.
That sure is pretty small amount of charging current...

"The Model A1265 (US version) can also be used to charge USB devices." Yes, you may have seen it charge some specific device, which you don't mention. But is it "dumb charger" compatible ? Have you (like I did) measured the D+/- pins with a multimeter to check for resistors or a short ? Facts like that would be nice ...

About the A1299: "It is not just a dummy charger with resistors signalling the charger type but instead has USB host mode chip that can do the standard current sourcing/sinking negotiation." Interesting ! I'd love to see a teardown/disassembly that confirmed that ...

The device was an N900, but in my haste to see if the charger from someone's iphone 5¹ was compatible with the standard, I'd forgotten the mini-USB to micro-USB adapter I was using didn't pass the D +/- wires.

With a normal micro-USB cable it does not function as a dumb charger. The N900 doesn't even give notification of a connection, and an N9 thinks it's mass storage and says there's not enough power to charge. So it turns out the in the US the Apple charger is just as shitty as ever.

¹ I have never and will never own an Apple device.