Derek Cohen (in Perth, Australia)
"There is a relief section at the end to enable the azebiki saw to drop lower."

I don't know what this sentence describes.

The top of that mortise looks frail. Personally, I would not risk that little end grain at a mortise top.

Explaining ..

First part: the azebiki saw plate is curved and cuts on the pull. The saw is designed to start a cut in the middle of a board. However, doing this would create a curved cut. Not helpful enough for a sliding dovetail. By having a cut out at the far end of the mortice (chiselled away), the azebiki teeth can cut from lower down, which would create an even (rather than curved) kerf. Simple, ain't it

Second part: the mortice in question is angled on both sides (unlike yours). As I explained at the time this was made, the legs angle away, and the sliding dovetail must be locked in from both sides. The mortice shoulders of the socket are further protected from breaking away by the covering shoulders of the mating tapered sliding dovetail.

Further ... you need the big picture here ... any twisting was minimised by bolts at judicious points.

Of course, this has nothing to offer your construction

Regards from Perth

Derek