I believe the magnitude of the force of friction between them does not depend on the relative speed of the two objects. When a solid and a fluid substance (including gases) are in contact, however, I believe that the magnitude of the force of friction on the solid does depend on the relative velocity of the two substances.
I think your contention about the different behavior of solid-solid interface and solid -liquid interface about the velocity dependence of frictional forces do not portray a real picture.
My contention is that in both cases the frictional force is velocity dependent and in case of different nature of surfaces
the frictional forces may vary due to smoothness of the surface in contact and relative motion.
The above idea took roots due to microscopic nature of the surfaces in contact and when they are in relative motion
the molecular level forces start operating and those interactions are temperature dependent which rises due to relative speed of the surfaces.
Moreover in solids the deformations in the surface terrain when the motion takes place is more pronounced due to the velocity(momentum transfer)
and as velocity rises the frictional force increases but later
as the surfaces get smoothed out the friction may decrease in certain cases with velocity.
Thus the velocity dependence in solid-solid interface of the kinetic friction is a fact and one should change the classical idea that the kinetic friction is velocity independent (what ever the nature of surfaces)
We show that the friction force varies with the sliding velocity in a manner that depends on the chemical nature of the interface. Surfaces terminated with the hydrogen acceptor and donor moieties capable of
forming H-bond networks exhibit a friction that decreases with sliding velocity, a behavior that is opposite
(see the recent work in this area.)