BLE HID iOS connection interval 15ms -> 11.25ms

[Mtz]

My goal is 11.25 ms for connection interval with iOS. With PC and Android i can setup it.

Following Apple guideline, I added HID service to my custom device(it works, i can send keys press). iOS decreased connection interval to 15 ms, when i added HID, but reject any request to set 11.25 ms (checked for iPhone 6 and 8). Are there any additional data or services characteristic, which iOS use to approve 11.25 ms ?

[Kenneth]

Seems like 15ms is a kind of hard limit yes, even from:
https://developer.apple.com/library/archive/qa/qa1931/_index.html

Kenneth

[Mtz]

But Apple have phrase in their guide:  "connection interval down to 11.25 ms may be accepted by the Apple product."