Not you're not missing anything. Yes its an inconsistency, although IIRC its deck height + 200, min 300' for Bristow. Still, there is a big difference between deck height + 200' and deck ht + 50'.
On the other hand, onshore landing off an instrument approach is in general different from landing off a visual approach (eg instrument, arrive at 200' and maybe 110 kts, visual, turn finals at 500' and maybe 80 kts. So the concept of differences for visual and instrument are widely accepted and necessary. If you propose to raise the ARA minima to deck ht + 200 you are getting close to removing any point in an ARA for some of the higher decks.
But, with the different rules at night for en route descending, needing to do an ARA at night is fairly common even when the wx is not that bad. A good ops manual would point out that descent should only be made below deck ht +200 if so required to get below cloud. It would be stupid to arrive at deck ht + 50 when deck ht +200 would get you in comfortably, but I've seen plenty of people doing it.
Pretty sure BHL ops man doesn't make this point, and I doubt others do (but stand to be corrected).