They tried this internally, and it causes a disgusting mess of problems.
"Is it correct that wagon transport has Horse movement type instead of Wheeled? I mean, in gameplay terms it is not that bad, as it makes this transport option actually attractive. But as things stand now, Horse transport has off-road capability which is similar to half-tracks and in some cases even exceeds it (can cross thick forest, for example)."
I want to say I am totally against this change, and wish for it to be reverted.
My reasoning is as such:
I really like horse transport to be useful. It always is looked down upon, and giving it some way to be superior in some aspect is a fantastic feature. If it has Wheel move, the same Wheel move as Open blitz, but horse moves 5 and Opel moves 8... the Opel is 100% better under all circumstances, and the horse goes back to only being terrible 'historical flavor' pick.
In the Spanish Civil War, horse transport is required. There are no Opel Blitz. So we are forcing people to use this transport, and its a very good impression they get from it. Because Spain does not have super extensive road networks, there is a lot of offroad, hilly, and mountain movement. And it's crazy useful to help the little Pak36 ATG to have horse transport that lets it move extremely well over difficult, roadless terrain.
Later on, yes most players will swap to Opel blitz options. They just see 8 speed, and go for highest speed on their transport, obviously. That's fine, 8 wheel is king at Major Road movement, as it very well should be.
But for those mountain scenarios that can and will come up.... if those horses are better at rough terrain, some people just might not automatically snub them.
I dont see horses as strictly pulling a wagon. (They didnt put the Pak 36 into a wagon, they just pulled it directly) I see 'horse' transport as 'pack animal' transport. Which should have superior offroad mobility.
As for horse vs halftrack, I find it hard to believe people will seriously opt out of HT for horse. HT is faster, better protected (something critically important in later war years), and some variants offer HT attack bonus traits.
So regardless of a bug, my opinion is that horse transport should go back to horse movement. It's good for variety of transport, it's good for low tech battlefields in rough terrain.
Pak 36 with horse now moves at same speed offroad regardless of transport
2 movement foot vs 5 movement wheel both = 2 movement over non road hexes
This feels extremely crappy, especially in the Spanish Civil War, which was not designed around horse transport being this bad at offroad terrain. I would need to add many more roads to the maps to compensate for this change.
If 5 is 'too good' retain horse type, but reduce speed to 4.