this method is not really clean for subdiv, and more unnecessarily longer to setup than manually doing the bevel and etc in the cage object at once…
corrective smooth will shrink the model, and get worst shading in those boundaries of the bevels, this guy doesnt show that here but i know because there is plenty of ngons in the boolean he is doing, and obvious results will happen…
stop believing in perfect and clean non destructive modelling workflows like this, we will not (yet) get that in blender and other 3d apps, and these is are just workarounds same as using boolean objects, retopology addons, and then subdiv similar like this standard workflow https://www.youtube.com/watch?v=jXh5ExOJuHk
if you ever need a good high poly and clean model to begin a concept model before doing retopology with subdiv for production (vfx, film, games, printing, etc) please use this addon, i really recommend it Black Mesh - Procedural Modeling Tool