Apple's Proximity Beacon Specification documents what it means for a Bluetooth Low Energy device to be an iBeacon. Within the specification there are several requirements identified. One of those is a fixed advertising interval. There have been many complaints that the interval is set too high which causes lifetime of a hardware beacon to plummet.
Defenders of the mandate believe Apple is doing what it does best: putting users first. This is good because it will thin the herd of beacon manufacturing companies by forcing them to figure out how to adequately balance power consumption with functionality and advertising intervals.
There's a bit of fear going through the minds of various beacon manufacturers. By adhering to the Proximity Specification, you essentially shorten the lifespan of your beacon to the point to where it's not practical for a widespread production rollout. There is also concern from peers in the industry and from support representatives that if your beacon complies to the iBeacon spec, it may work today, but not necessarily in the future.
That's a huge area of risk for any company operating in this arena. The problem with this is that it's not likely to be enforced by Apple at an OS level. The difficulty is created by the fact that the advertising interval only affects how often a device will potentially see the beacon. The word "potential" is very critical here. The best case scenario is that the iOS device will see all advertisements of a nearby beacon. The realistic scenario is that it won't see all of the advertisements. There are multiple reasons for this: 1) the antenna on an iOS device shared between WiFi, class Bluetooth, and Bluetooth Low Energy and some advertisements get missed; 2) the iOS device is busy doing other things and some advertisements get missed; 3) there is environmental/airwave interference that causes some advertisements to be missed.
It would require iOS to put a lot of priority in listening to iBeacon advertisements so that it could competently know when a beacon was in violation of the advertising interval for Apple to be able to enforce it. Without that, the fixed advertising interval mandate seems entirely useless. That part should have just been a suggestion.