Imagine you have a (hypothetical) method that can exactly capture the van der Waals interaction. Then when you do a geometry optimization, you are neglecting the quantum and thermal fluctuations of the atoms, and you end up with what is called the static lattice approximation. As quantum and thermal fluctuations tend to expand the lattice, then you would expect that an exact method would predict a geometry that underestimates the experimental lattice parameters. This is true if experiments are performed at room temperature, but it is also true even if they are performed at zero temperature because of quantum fluctuations.
Additionally, layered van der Waals compounds tend to have a relatively large thermal expansion coefficient along the stacking direction, so for these compounds you would expect an even larger underestimation between an exact van der Waals calculation and experiment.
Putting this together, if you have an approximate van der Waals method that exactly reproduces the experimental lattice parameter, then the van der Waals approximate method is in fact not that good because when you added the quantum and thermal fluctuations, you would end up overestimating the lattice parameter. On the other hand, if you have a van der Waals approximate method that slightly underestimates the lattice parameter, then that has a good chance of being a better approximation, because adding quantum and thermal fluctuations would take you closer to the experimental value. To confirm this, you should calculate the effects of thermal expansion, for example using the quasiharmonic approximation.
I have no experience in SCAN-RVV10, but underestimating the lattice parameter by 0.15 Angstrom (I am guessing the units here because you did not provide them), actually sounds pretty good.
