Not necessarily... Thompson claims 33" pitch for what would essentially be a 1-1 configuration. I believe the Diamond seat is pitched at 58" for 2-2 on the 757 (but it might be 55"... not certain). So, using 58" pitch, at 4 rows, you have 232" of cabin space allocated to a 16 seat J cabin. At 33" pitch, the same section could theoretically accommodate 7 rows at 1-1, for a 14-seat cabin. The A321XLR and 737-10 don't have exit doors forward of the wings, so an operator could plan enough cabin space to keep seat count the same with only a small density penalty.

I think the VantageSolo looks pretty tight, and no doubt it will be referred to as a "coffin" seat, but direct aisle access for all seats on a narrowbody, at an international business class-standard density, is highly desirable.