Well, go and walk up with rak against upgraded firing position and see for yourself?
These two are suppression area denial, they do nothing damage wise, unless you're pinned for a long time and accuracy penalty kicks in.
Hell, because of how suppression works and the fact that rak doesn't get penalized by it, rak will take little to no damage at all while suppressed for long enough time to kill FP.
I feel that the Incendiary (H)MG42 you know and the one I know, are very different things. The situation described earlier made worse by the fact that the AT gun was within the mid-range for the HMG42.
The bunker may never have fired, but the Inc (H)MG42 would have vaporised a Rak.