Thank you all for support and the good ideas.

Although I have reasons to believe no one found out the solution yet, I'll test all suggestions you guys made and get back to each of you.

By now I gotta say that I'm pretty sure the Low Gravity MIGHT trigger the same issue I've seen on tus schemes.
I was playing a new scheme based on HostingBuddy's shopper when I noticed rope was terribly slower after I used LG in previous turn.
However, even though I tried hard to replicate the issue, the rope speed (or gravity) seemed to reset to random values in a range after each time I used LG.

This is very very weird. It has to be a bug in code during gravity reset AND passed along through scheme files.
If that's correct, maybe I could be able to catch the exact bit changes in HB's scheme file.
If not, I hope anyone can debug variable values if I prove something is going on.
I'll prepare all tests with small maps to upload here during the week.

[TLDR: skip to words in bold]

Can anyone explain me why is normal gravity a little weak in some schemes hosted by TUS-WA website compared to HostingBuddy schemes?

It may seem almost unnoticeable. But it makes big difference while roping.

First of all, I'M NOT A NOOB!

I first noticed this years ago, when playing roper scheme for the first time and then every once in a while.
As I was a noob, I just thought I wasn't good enough to play roper and that maybe I wasn't focused enough.
Now, however, my roping skills are much better. I play rope race and WxW a lot in HostingBuddy schemes.
So I finally decided to play tus leagues then. But soon I noticed how roping was messed up in tus schemes
(Roper and Shopper, so far, but not WxW Shopper).

These are the issues:

1- The roping becomes "weak". It takes more strengh (or time) to build movement and speed during roping.

2- At same time, roping gets more "inertia". The movement and speed already built in roping last much longer than usual.

It took me a few game losses to figure out that only a lower gravity would reproduce both issues.
Low gravity makes movement slower, requiring then more time (issue 1) while also makes them last longer (issue 2).
It seems like normal gravity is set up around 70-90% of that in HostingBuddy schemes.

I deactivated RUBBERWORM to compare schemes from tus (ROPER) and HostingBuddy(SHOPPER).
But the roping behaviour still feels different for each one as explained above.
You can easily feel the difference when trying to achieve max speed.
You'll notice how hard it is to gain speed in tus schemes.
It actually seems like there is a lower frame rate or lower max speed limiter.
Also, in tus scheme, you may notice differences when you hit a wall (you bounce much longer in lower gravity) or flying (you fly much longer too).

Unfortunately I can't attach the game files used in my tests (attachment restricted to < 1024 KB).
However you can get the schemes directly from tus and HostingBuddy to test them by yourselves:

https://www.tus-wa.com/schemes/scheme-3/

Hosting Buddy:
[attachment=1]

My game version is 3.7.2.1 - Steam.

Can you guys explain/fix this?
Which scheme should I play from now on?
For the record, I like the higher speeds from HostingBuddy schemes.
But I wanted to play tus leagues as well.

So now I'm going to play leagues with my own fixed schemes (modified HB scheme).
Basically I overwrite HB schemes in such a way reproducing all settings from tus schemes - and yet the speed doesn't change. You may donwload fixed versions here:

https://www.tus-wa.com/schemes/scheme-2020/
https://www.tus-wa.com/schemes/scheme-2021/