Actually, it's not particularly good advice even for writers. It's advice to "do things my way, not your way," based on a weakness which the author lacks, but to which not all worldbuilders fall prey; i.e., building the world at the expense of the story. He'd spend his time better giving advice about how to approach his own strengths and avoid his own weaknesses - the only topics any of us can truly give useful advice on.
Tolkien would never have written the Hobbit or LOTR if he hadn't had his language- and world-building hobby. Diana Wynne Jones makes worlds the way other people make sandwiches - vivid, realistic, self-consistent worlds and series of worlds about which the reader learns just the right amount. I don't know how much work she puts into the process of creating them, and I don't need to know. The result counts. How you get there doesn't.
There are nine and sixty ways of creating tribal lays, and every single one of them is right. Some people have to have the worldbuilding and some people get bogged down in them and some people can't make them at all, and make a virtue of it. There's no point in making hard-and-fast rules about any of it. Personally, I have to overprepare for every session I DM, every public talk I give, everything I do that involves prolonged speaking. Other people can do satisfactory games at five minutes notice.
More power to everybody. Do it the way that works for you, not the way that works for somebody else.