Google's Nexus 4 has an LTE chip, but why is it disabled?

It turns out that Google's new Nexus 4 contains a hidden LTE chip that can be activated using a simple hack. But, there's a good reason why that LTE modem has been disabled.
The modem was initially discovered by the eagle-eyed folks over at repair firm iFixit, who found a Qualcomm WTR1605L seven-band 4G LTE modem on the mainboard during the course of a teardown.

Then, technology site Tek.Gadg posted a video showing how to activate the LTE modem using a simple keystroke command, and showed the sorts of speeds you could expect from the hidden modem.
If the Nexus 4 has an LTE modem, why has it been disabled? According to LG, the manufacturer of the Nexus 4, it has been disabled for cost reasons.
Speaking to TechRadar, an LG spokesperson confirmed that the Nexus 4 uses the same Qualcomm Snapdragon chipset as found inside the LG Optimus G, and that this chipset is only available as a package with the processor and modem combined.
But Nexus 4 owners don't get a free LTE modem. While the Nexus 4 has LTE capabilities, according to LG, "it is only effective when combined with other essential hardware parts such as a signal amplifier and filter in order for it to work." These components have been omitted from the Nexus 4 in order to reduce cost.
So, given this, how do we explain the video? My guess is that the LTE modem may still be able to work in areas where the signal is strong enough to not require the signal amplifier and filter. This explains why some Nexus 4 owners have managed to get the hack to work, while others have not.
Image source: iFixit.