I don’t mean to be negative here (and I will actually remove this post if folks don’t think it fits in with what I am sure will otherwise be a love-fest for this tip, and probably rightly so), but I think this statement at the end of the post is being downplayed a bit.
In your simple demo, the tip seems to add at least three seconds to the initial load time. So, in a real app, it could easily add half-a-dozen to even tens of seconds to the initial load time. (It was quite a while ago, but even Emmanuel himself advised against this tip for that reason.)
While some (most?) folks might agree that front-loading all of the load time is a better trade than spreading the load time out across the tabs when they are loaded for the first time (and only the first time, so an app that uses the tip or an app that doesn’t use it will perform the same after the bigger initial load or smaller loads across the tabs are done), I have worked with a number of UX folks throughout my career who are definitely opposed to the longer initial load time.
To be clear, it’s still a great tip, and one of the best parts is it can be tried in an app with little effort to see if the trade off (initial load vs. smaller loads across the tabs) is worth it. I have seen cases where it is not, though, and again, it felt (maybe only to me) like that pretty important aspect of the tip might get missed.