Pretty sure I have seen my athletics rise while using throwing weapons on horseback so...
Except for the fact that these numbers don't necessarily translate directly from real world to game, they are essentially just placeholder numbers so the game can do math for things like damage. So it really shouldn't matter, unless the horses are actually traveling that fast in game, in which case nerf please.
well, it does seem to me like lengths are in centimeters, so length 120 for a weapon means that its reach is 120 cm. 2,4 m reach for spears, and so on. Horses being in the 500 kilo range, their speed ? Km/h ? Starting sumpter is some 34 km/h. High speed ones are in 70s. Conversion from meters to second to kilometer per hour is 3,6, as 1 m/s = 3,6 km/h. A made-up horse has 75 speed. If this is 75 km/h, it translates to 20,83 m/s as base.
Then we will add riding skill which adds to its speed. With horse archery, 200 riding skill is not difficult to get if you have 7 endurance due to smithing. I deleted my archer smith char a few patches ago, and I with the noble bow managed 105 m/s shots when I released 3 meters from target them approaching, not on a horse.
105 m/s translates to 378 km/h or 234,87 m/h = 378 feet/second.
Ballista at close range has an excess of 100 m/s too.
In the video that debunked the plate-killing power of the english longbow they were using 80 gram (0,08 kg/0,17lb) arrows. 72 kilo draw weight. (160lb, 1 lb = 0,454 kg) the arrow after 10 meters had out of my head, velocity of 53 meters per second.
Other, like great crossbows, even heavy ones using bolts 3-4 times as heavy as the warbow, 570 kg draw weight (1250 lb) with a bow 1,5 meters long (5 ft) it shot bolts heavy from 0,22kg to 0,38 kg (0,48 -0,83 lb) none of them exceeded or even reached 60 meters per second. 'Muzzle' velocity measured varied from 51 - 58 m/s or so. Then you have things like higher air resistance affecting effective range. There were bigger crossbows than this, with up to 1,9 m in bow length, with proper composite bow, Interesting things could happen. Velocity and the bolt weight.
With these, a 25 kilo pavise is a no brainer, but the big composite bow crossbows were no joke.