I don't think this is reactionary on Intel's part: they have quite a few other customers than Apple, not to mention they're the current darlings of the DIY PC community. I think that Intel just has a yield issue, whenever you change manufacturing processes to become smaller, more power-efficient, and yet still deliver a more powerful CPU...well if it was easy they'd just do it all the time!
Apple has always been about controlling the ecosystem, hardware and software. They were forced to go to Intel when the PowerPC chips weren't able to deliver the speed and power that Apple wanted, so they went with the 800lbs gorilla who was also beginning to embark on their aggressive Tick-Tock updating calendar of every 12-18 months providing a new tick (die shrink) or tock (new architecture) CPU and chipset. That was about the pace of improvement that a company like Apple would want.
Early on, Intel was adhering to this aggressive schedule, and even giving Apple either custom versions of chips, or providing them with chips earlier than their other customers, or both. Now they're clearly getting their chips about the same time as everyone else, and couple that with the broadened time lag between Haswell and Broadwell going on 24 months, and you can see why Apple may be a bit frustrated with Intel. Especially since Apple have now launched several new product lines since the transition to Intel (iPhone, iPad) which are now on a 12-month update cycle. I think Apple would like their notebooks and desktops to be on a similar upgrade trend (it makes for a nice predictable bottom line, which is important to investors).