Checkboard, well put.
When I did my multi years ago it was common to land with one feathered on the last sortie. It seems to have been phased out. I remember doing it with some students when I gained ME training approval 8 years ago but the instructional value is marginal and as you say reduces safety margins with no compensation.
I think the time used in this procedure could be better employed.
The CAAP 5.23-1 seems vague on this. CASA regulating for safety...