Very interesting. I've never been in the military so I really can't opine to a rationale behind what would be best for their fitness needs. I've always associated their conditioning requirements with "beyond bad ass" and I'll leave it at that.
I've done a lot of strongman implement training. To be frank, I considered it "heavy" metabolic conditioning - it is GPP at it's finest. The size and weight of the implement used should be relevant to your strength and strength experience levels. I can use the heavier implements, but it's not necessary to get the affect for my own training. I did a rendition of the Arnold timber carry with an 800lb+ implement a few years ago that left my traps and shoulders sore as all get out even though I only took a handful of steps with the object. Doing the carry with a lighter weight, or flipping a smaller tire, for up to 90 seconds was more along the lines of what would benefit what I want to do.
I regularly include carry and drags, and stone/block lifting/carrying in my training as they are great functional fitness that takes the heart rate and pain threholds into new territory. That new territory has to be metered or one runs the risk of injury - so I don't do these movements very often.
I can understand the reason why the person suggested this sort of protocol. To be frank, there are a half million ways to skin a cat. None, in my opinion, are any better than the others - they're just different. A person has to try lots of stuff to find out what works best for them. If that makes any sense?
All the best,