I missread the OP. :# I think he meant inflating low poly. It's what I meant. Doing it to Hipoly is indeed weird. Inflating low poly along vertex normals to bake world space normal map on the other hand is where low poly itself become the cage . That way it works in many renderers that are not supported by regular texture…
Generally, you want the shapes in the high and low poly to match as closely as possible - this means that often the low poly will either be exactly the same size or both slightly bigger and smaller than the high. For something like a cylinder, the low should intersect with the high in a vacillating pattern. Here's an…
My guess his advice goes to cage model rather than low poly itself. Or it may work when you bake world space normal map to be re-baked into tangent space in a separate pass . Especially when you use some 3d party renderer that is not directly supported in package bake tool. For world space normals the actual shape of low…