All of the steps listed in the walkthrough are important except for the last step, which is more of a convenience.
Flashing the radios is necessary because Google disabled the ability to use LTE after the .33 radio. So if you have a newer one, it won't work unless you flash a radio that allows it.
The build.prop edits are necessary so that the device knows how to pull lte signal.
The dial code menu option is necessary in order to enable LTE
The apn edit is necessary so that the device knows from where (ie the carrier) to pull lte signal.
Because the dial code menu option resets every reboot, the last part of the walkthrough is to prevent it from doing so. However if you feel like redoing it each time the phone reboots, then you can skip the last step.
Some of the videos you talk about not doing all the steps might be older and made before Google disabled lte in the .48 radio. So that would allow them to not need to flash the older one because they already had it.