First, just for for clarification, by "alcohol" fender3x (USA) is referring to what we know as methylated spirits. And by methylated spirits, I'm talking about 100% industrial methylated spirits, not the 95% stuff you get at Bunnings or the supermarket. (I have carried on about this in a number of threads)
Waxed vs dewaxed, as used in our pursuits of guitar finishing, the reason for using de-waxed is about compatibility with other finish materials that may go over it. For example is the shellac is used either as wood sealer or to get a bit of colour under another clear coat, it needs to be dewaxed or another material (paint, poly etc) won't adhere to it.
I you never intend to apply anything over the shellac (other than more shellac) there's no reason you can't use a waxed shellac as your finish. However IMO, shellac on its own is not a top choice for a guitar finish for a number of reasons.