@ckchessmaster eap610 which I tested worked flawless. It is other eap6xx models which seem to be broken. Nobody with apples on their head complained when eap610 was used, apple is often the cause and its owners are mostly clueless people believing they've got a high tech phone which cant compete with $ 100 phones, thats why US had a need to attack huawei which is better in everything compared to apples. However, when one supports rogue companies and buys its products, one should expect issues with it, if it were my network, I would urge the client to contact his fruits support, that is at least what one would expect from thousand dollar phone.

  @ckchessmaster 

Have you tried to disable 2.4Ghz but only use 5Ghz SSID?

If other devices can get normal speed, it seems more like a compatible issue, not the EAP hardware issue. 5Ghz may have a better performance in this porint.

You can also try to update the firmware of the EAP, and iOS version of Apple devices.