I understand this will of course add strength and for various styles it is also a necessary visual component. But for certain watch pairings I'm really fond of the sleek look of no stitching at all. For example the "Luther" from Bas and Loke (see below). Is this look possible with glue only or is there likely some stitching inside and then covered by a non-stitched cosmetic veneer?
Without knowing more, it looks to be a glue only strap. Personally I would never use this with a regular buckle as this stresses the strap a lot more. Its useful life will likely be shorter than a stitched equivalent. In my opinion, a deployant style closure would last much longer with a glue only strap.
For occasional use such as with a dress watch, I wouldn't have too much of an issue, but definately not a daily wearer.
You can compromise by creating a deep crease, then stitching within the crease using thinner than normal thread (using thread of the same colour as the leather). This way you'll only notice your stitches up close. Crease again over the stitches when complete to hide them.
For an actual hidden stitch, see the course 'Techniques of hand stitching: Advanced skills'.