Anyway, here is the problem (and I'll do my best to explain it).
When you set CC to, for example, at 60 km/h, it's all fine with the RPM gauge. However after the truck manages to achieve that speed something like 300 RPMs are lost; it's like the clutch slipped or something. As soon as you press the throttle the RPM goes (without pulling) up to the cca 1400 RPMs and then starts pulling effectively. Basically, there is an empty space between pulling range and cruise speed.
I do think it's a bug because when you reach 60 km/h at 1.300 RPMs, the truck should remain in that range unless there are some changes in the terrain that would affect the speed. Also it should raise as the truck accelerates or drop down as the truck decelerates (unless it's using full power)
Here are the two photos; in the first photo the truck has reached the desired speed (60 km/h) and I'm not using throttle at all. In the second photo I'm using throttle 100%. The problem is, what happens in between? It's cruising at around 1.200 and after I "floor it" nothing happens untill 1.500 PM.
Perhaps I'm not familiar with this or that's completely normal with certain gearboxes or whatever; but it's still a bug in my head until someone manages to explain it to me



And the overlapping of the two, to show you what I mean. Marked in PINK color

*Any additional info is more than welcome*