737 jockey
“As in my example of a CATII minima of 105 RA, I presume the CATIIIa would be higher than 50, perhaps 55...”
On a CAT2 approach the minima may be different because of the terrain on the approach, for CAT3a the minima is always going to be 50 RA because you will always be over the runway, therefore if this minima is set in stone, why produce a meaningless CAT3 plate.