What TP is saying is "referencing" isnt necessary. And if only running the part in 1 set up or if no mistakes are made, that is probably alright. However if there was an issue or recovery was needed, I am not sure how he would implement that. Not saying it cant be done, I just dont know how, yet.
The way I did it prior to having switches on my machines was to move the X & Y axis to their most negative travel and the Z up to the top. Hit ref all home. All machine coordinates will then turn to 0. If your software limits are correct (if you set them up), you can keep your machine pretty accurate, not to the .002 but good for most work.