These are good questions! You’re right that it’s easy to find yourself in the grey area between “training” and “recreating”; this isn’t always a bad thing and the two overlap pretty easily. A 2-3 hr hike can be “training” but the distinction I like to draw between those two is that training is done with intention. This intention can be to maintain your Aerobic Threshold, both by not exceeding it, but also by keeping the effort up high enough. I wonder if this might be of help to you; oftentimes with hiking the effort can be pretty low (below AeT), at which point the gains start to diminish. Spending more of your hours each week focused concertedly on an AeT effort, hiking uphill, may help to iron out the volume of “training” vs. “recreating”.
The other thing I would say is that if your goal is to improve skinning pace while split boarding, it would be good to look toward eventually adding in some moderate intensity work as well; this will provide a means for you to be moving faster for short periods and training those muscles to move more efficiently. In this way, over time they will be able to operate at a faster output while still maintaining an aerobic effort.
Bottom line: as long as you recover from day to day and aren’t feeling compounding fatigue or soreness, you’re not doing damage. BUT, you may want to consider making more of your sessions more specific/focused on the AeT and eventually up toward the AnT (Z3 intervals) if your goal is to improve economy for the riding season.