If you really want to look into this, here is how DTA is supposed to be calc'd.
Fly-over waypoints make you set many parameters, so you can fly over them, fly-by waypoints give the FMC the idea of what to do, and it handles the turn...
you can see why included angle TF legs have such unusual results...
there are several early versions of FMS, which would do a flyover anyways, then turn to get back to the TF leg, this is one of the reasons why the containment's are so odd looking...
this is an example of what the procedure design might look like for that turn you were looking at...
fly-over
vs fly-by...