BT-5/BT-7 vs M2A2/M2A4 speed

[Happy Demon]

So I was watching videos regarding tanks, and the BT series was kinda interesting. High speed tanks with designs from a sports car designer, so I decided to jump into this game again. I didn't bother linking up my old account, so I went for Steam account and started over.

I enjoyed playing the BT-5 for a while, though I kept to low tier, so I could get some good driver levels, get it as speedy as I could. But eventually, I decided to check the tech tree. I saw that the BT-7 was the last Soviet speed tank, so I decided to look around the other tech trees for a viable multi-tier speed tank tree.

However, I noticed a thing, the BT series are capped at 60 km/h. A bit strange, with it being capable of 72 km/h top speed. The BT-5 and BT-7 are virtually indentical, despite the BT-7 having a more powerful engine, which should've given it more speed. But it only results in a 1 km/h difference. Big on heavy tanks maybe, but insignificant on light.

Looking through the others, I found the Germans, they do like their autobahn, with a max speed of 80 km/h on their armored car, and 100 km/h on the Puma. Makes sense, they're armored cars. Speed is their thing.

Then I found the Americans.
Why is the M2A4 faster than the BT-7?
Even just checking Wikipedia, and while it doesn't specifify which M2 tank it's referring to, has the max speed at 58 km/h. Which is even lower than War Thunder's BT-5, which was 59 km/h.
But the M2A4 has a max speed of 63 km/h. This tank is historically slower, but here it's faster?
And then you have the M2A2, with a max speed of 80 km/h. Why is it so fast?

Is this balance? Did they buff the speed because of their lacklustre armaments? Why does the BT series have their speed butchered while the M2 series are jacked up to such ridiculous levels? Is it to force the US into having the speedy tank niche? They didn't nerf the Germans though, they got to have the highest speed in the game.
Are the US tanks even capable of reaching that speed? If not: Why give them speeds they cannot reach while the BT series have their max speed reduced? They end up capping their speed constantly. Despite being designed for highly mobile warfare, where reaching the strategic locations first is good.

[DapperSpino]

I'll tell you that the BTs are 100% faster than the Stuarts, they might not have the same top speed but BTs will accelerate extremely fast, though the top speeds you'll have to do your own research on because I don't know what the top speed for them was.

[The Wiggly Armed Man]

60 kp/h is already really fast and the acceleration of the BT-5 and BT-7 is amazing.