I have a stool sample like that. I shared it with my doctor last time I went in for a physical he laughed his a$$ off.
Yep, he was using a router to cut his mortises, which is fine but when he did his tenons he cut them on the table saw again this is fine but he was cutting them about 1/2 narrower then they should be so he didn't have to take the time to round the edge of the tenons to fit the mortise, this left about a 1/4 gap at both ends of the mortise. So if his mortise was 1 1/2 inches he was cutting the tenons about an inch so he didn't have to round the edges, but like I said this left a gap at both ends of the mortise.