I can give some anecdotal support for the metcon type workouts helping endurance and recovery. Each year my family spends a week up in Yosemite. I hike Half Dome every year. Before the last trip I had been doing all metcon (crossfit style) work for about eight months and ZERO classical endurance work.
None of my workouts were over 45 minutes and I worked out between three and six days a week. My time for the hike was somewhere around an hour faster than I had ever done it before. Most importantly, I was honestly not sore the next day or the day after that and I slept great that night. I realize that this is not a multi-day super hard event like is being discussed here, but it is about 8 hours of pretty much non-stop moving. In past years I was training for Triathlons and road cycling and mountain bike racing. Again, this past year was my strongest and fastest and most comfortable trip ever, and I felt like I could have done it again the next day. I am sold on the program. Take it for what it's worth...