I have watches some videos from that guy in the past. He is usually entertaining but he is also not a historian in terms of a university degree or something similar. So he is a layman, but he also never claims to be a complete expert. A lot of his points are pretty speculative (which he usually also says). So everything he says should be taken with a good grain of salt.
We don't have two machine guns in a the same fireteam by default. Our default fireteams look like this.
Charlie1. AT
2. SL
3. Marksman
4. LMG
Delta5. AT / Engineer
6. Medic
7. FTL
8. LMG
Apart from that I think some people misunderstand the role of a mg a bit. You are not really supposed to give precise fire on those ranges. You are supposed to effectively shoot the area of the enemy. That does not mean you are aiming for specific body parts of individual enemies. This can be done very well with iron sights. At least for me, this is also easier with iron sights. You get less tunnel vision and this makes me keep a better eye on the area I want to shoot.
Some of our members can confirm that I can be very effective like that.