[aerohead]

If they were serrated, there'd be a small difference in pressure at the 'tips', compared to the 'short' pie-piece voids.
Technically, that's a setup for vorticity and noise at the staggered separation line, and it would rob some pressure recovery overall.
According to NASA Photo: E-38096, from 1981, we'd likely see zero longitudinal vorticity as can be seen ( tufts ) on Project Shoebox.
By the way, NASA'a boat-tail appears to be cribbed from Paul Jaray & Associates' 1921, softened and boat-tailed square-cylinder, tested by Wolgang Klemperer, at the Zeppelin Werkes wind tunnel.
And it's delta-Cd varies almost perfectly as described in SAE Paper # 2020-01-0673, by Jeff Howell et al.. ( Cd 0.2429-predicted, vs Cd 0.242 as measured by NASA ).