Liquid simulation did not have instant caching.
A modular baking allows to bake FLIP particles separately from mesh which is faster, less memory consuming.
Mantaflow is doing liquid and both.
Choosing a modular cache for smokes too was a way to be consistent.
It is also less memory consuming to bake noise separately for smokes.
So, it was basis for mantaflow until its merge. At that moment, several users requested Replay cache.
So, it is a recent caching method and does not have desired stability, yet.
Modular method requires to bake. But you can pause bake at any moment to preview how it goes.
And if everything went well until frame of pause, you can press Resume button.
That is not very far from instant caching.
Changing a setting was also invalidating cache in 2.81.(Messing it up or erasing it)
In 2.81, you don’t press bake button and pause.
But you have to go back to first frame and play animation to obtain a valid cache.
Also, 2.82 has higher standards. Resolution of domain is higher. CFL number and Adaptive Timesteps are useful to stabilize liquid simulations but are slowing down baking.
You can increase CFL number to its maximum and disable Adaptive Timesteps to speed up baking of smokes.