Yeah, the bolster makes things less awkward for sure. It's easy enough to fit, pretty much like a metal guard but easier to file. Just the front 1/4" of the slot is fit snug, the back of the slot through the bolster is milled out wider to make fitup easier. It has an alignment pin on either side of the tang as well, going through the spacers and pinning the handle pieces together. Using phenolic for the bolster rather than metal keeps things pretty light.
It's a bit similar to "wa" handle construction but more western-ish.
I mortised the handle scales because I like how snug a fit I can get that way, and how the tang can extend pretty much full length inside the grip to bring the balance back a bit. (And because it's a PITA broaching out that long thin cavity if a single block is drilled into.)