Since you've tagged me, long have i stopped considering what should be good or bad for our men in uniform because at the end of day it's all wishful thinking, at least for me. I keep myself limited to the small arms tech only nowadays.
Based on the techncal points i believe they aren't keen to adopt to Amogh or JVPC is because rounds like 9mm can penetrate straightly through thin walls, without much wear-tear fragmentation to the bullet while a lighter 5.56mm round could get fragmented-tumbled if fired through somewhat penetrable walls, so that way 9mm could have some advantage in confined space CQB needs that they have usually on boats - one of the many reasons they kept sticking to Sterling though ideally should've switched to MP5 long back, or better MP9 or whatever suits them idk.