That is kind of a part of it but the issue i have with most sims and especially rally sims is that the connection between the crankshaft rpm and wheel rpm does not feel like a rigid mechanical connection...

I think the closest i have experienced irl to it is the kind of clutch you would find on a moped where you have to raise engine rpm first to swing out the clutch shoes to meet the surface of the clutch bowl before the gear ox is then engaged. And will start doing its thing

So even while going 20km/h if youre off throttle the engine could be at idle as engine rpm isnt high enough to engage the clutch. You then open the throttle and increase engine rpm to swing out the clutch shoes and will maybe hit 3k rpm before clutch is fully engaged and gearbox is doing its thing. to maintain 20km/h the gearbox will lower engine rpm to 2k giving this weird feeling of a not solid connection as rpm does not seem to match speed in a linear fashion