So. Arch-Militans get their first Heavy Weapon Training (not counting backdooring in with Flame Weapon Training at rank 2) at Rank 4, and Bulging Biceps at the same rank, for 500 XP.

Voidmasters get their first Heavy Weapon Training talent at rank 4, and can only pick one to the Arch-Militant's 2, makes sense.

But they also get Bulging Biceps at rank THREE, for only 200 XP! And the eratta doesn't mention anything, what's going on here?

Void-Masters, being officers, ships hands, stuff like that, obviously are used to lugging around equipment and gear for their Rogue Trader