Thanks for your question. The ME workouts are designated as such. The long weighted hikes are not intended as ME workouts. I’m not sure what the UA site site says about ME. There is a good chance they have changed what I originally wrote. For a complete discussion of ME, I suggest you read this article https://evokeendurance.com/muscular-endurance-all-you-need-to-know/
The ME workouts use a very heavy weight. Heavy enough that the local fatigue in your legs is the limitation to how fast you can hike very steeply uphill, not your breathing or heart rate. The long weighted hikes with 10 and then 15% of your body weight are aerobic capacity building training, not ME workouts.
We do not use long hikes with heavy packs and have never recommended that sort of training. We do not use that for any of our mountaineers or our military athletes (who have to carry considerably more weight than mountaineers. Over the past 20-some years of coaching this stuff, we have found that the combination of the very heavy ME sessions (done as per the instructions) and long, moderately weighted hikes produce the best results with the least chance for injury and overtraining.
I hope this helps.
Scott