Timesteps and Substeps in fluid sim are aiming to prevent from leaking due calculation, but result is frame by frame shape of liquid that is totally different object (in meaning of topology) from frame to frame ... so I thing there subs are not store as shape (vertices) for reuse for DP.
Substeps in Dynamic Paint are able to be recalculate in-between frames from object loc/rot/scale or vertices, but that is not happening here in case of fluids ...
You can simply to check that if you go to Output Properties > Dimension > Time Remapping > New 400 ... as you can see, Cube has a statement for every frame ... Fluid object each fourth.
So ... the only one thing that can be a solution ... is to change a speed of fluid-sim to slow-motion ... Bake DP and speed it up or render each n-frame.
Easily to set with $ FlipFluid addon by Speed value, but with blenders fluid solver I tried to lower Time Scale, that make sim slow, but result is totally different from original sim ... it can be just I don't know how to use it properly (but I can't find any tut covering slow motion with Mantaflow). Sorry