nothing in this hobby is Bible (well, except maybe thermostats). it's good to make sure your new snake is eating consistently, but i think the three successful feedings "rule" helps new owners focus on the snake's needs first instead of their own wants.
i handled Coffee Bean two days after i got her and moved her into a completely different set up, and she ate that night. this has more to do with my ability to read my animals and my experience.
honestly you can handle the snake however soon you please, but there's a history of new owners running into issues doing so (as documented on many forums), so sometimes it's best to help new owners by offering experience in the form of a "rule" which is more of a guideline anyhow.