I initially started with muni and now have done trial, freestyle, hockey, track, basketball and a little road.
Freestyle to Muni:
About 3 years ago I started freestyle. Is was no surprise that the freestyle improves control, but I was initially surprised how much freestyle helped in my muni: I got better controlling short cranks, freemounts became super stable in any terrain, my downhill improved with more precise control.
Then this last winter I trained much more freestyle than muni (freestyle about 3 times a week and muni maybe once a month, so less than the last years). This week I was very (pleasantly) surprised as I started training for the muni season: I was expecting to be very weak and out of shape, especially on climbs. But in my 2 muni tours this week (my standard mountain route with 800m vertical) and my XC route but with multiple short steep climbs of 18-25% grade, I was actually stronger uphill then the month of April the last years and close to my peak training last summer!!
My guess is that wheel walk and other freestyle builds up the back muscles and general control, so I have more control at slow speed and can put more power into the pedals (i.e. I waste less energy flailing for balance). And I think drag seat in particular builds my leg muscles. As an aside I also think my strength training has benefits in pulling the handlebar on 20%+ grade. It was really nice to push with really high power on my 29" uphill with 110mm!! For the steep 40 meter section I initially had 2 dismounts. Then second run I had one dismount and that only because a car was behind me so I was a bit nervous and then stopped to let it pass. The next day I rode it without dismount (albeit on my 27.5 with 137mm cranks) and was almost easy. And this is a climb I have never made without a dismount!!!
So what are your thoughts? Freestyle and flat definitely have crossover training effects? And obviously my freestyle wheel walk (I can now ride 1-2 loops around tge gym in wheel walk) helps for track 1ft and wheel walk.