As you note; strength training makes up an important part of training for XC and Skimo. Midseason, however it can be tricky to use and see gains from it on a short term basis. The Advanced Skimo plan does not anticipate a 6 week midseason break. During such a long break it could be worthwhile including strength training. ME will be the most specific form of strength work for these events BUT you are also presumable doing some high intensity interval training during this break, which is even more specific and has its own ME demands. I would not normally recommend a focused ME block mid season. I did once use a late season 12 day/4 workout ME block with very good results with Erik Bjornsen but did no other intensity. I did similar once with Torin Koos with great results. Both these guys had exceptionally high work capacity.
With Mike Foote how is not prepping for World Champs and a slew of other races in March we are doing 2 short general strength workouts/week. These are mainly core and low rep high weight strength. He is also doing aerobic intensity 2x/week.
I’d be inclined to use this break for strength maintenance using a max strength protocol 1-2 short max workouts a week. This will least impact the important high intensity aerobic work yo need to be doing
Sorry if this sounds confusing.