Ummm, I don't understand.
The bottom of the Moto X '14 has about 9.8-10.1mm gap/bezel from the screen's edge to the bottom of the phone.

That gap is taken up by the speaker.

Most devices with Capacitive buttons need around 14mm's of gap. And don't have to contend with a speaker.

The Moto X '14 does not have space for Capacitive buttons. If it did, you would expect the device's length to increase from 140.8mm to at least 148mm. Or about the size of the LG G3 which has a 5.5inch screen compared to the Moto X's 5.2inch screen.

I'm not sure if I'm explaining things properly for you.