Did a partial de-construction. No additional tape or leather strip.
I'm confident that ,at least for this particular version, the cover leather is cut slightly oversize, stitched and then trimmed closely.
I tried a test piece and was surprised how accurately the trimming could be done. Shears have to be good quality and sharp.
You can ride the point of the shears under the flap and tight along the stich line as you cut.
Thanks for taking the time to help.