Infact i have not tried blender 2.81, i am currently using blender 2.80 which is fine where the scrap brush is working fine.

scrape brush is most used brush for trimming and hard surface modelling,
Scrape brush is not supposed to dig in holes like that.

I think i understand what is wrong with scrap brush and this is associated with all brushes.

scrape brush tries to level a surface such that it trims upper surface to match with lowest one, on the other hand flatten brush averages the gap between different surfaces.

HERE is whats going wrong

scrape brush is miscalculating the lowest surface thus it keeps digging into the mush .
similarly lets talk about clay brush. Clay brush is also miscalculating the difference in high and low surface and it fills the gap so fastly. i mean if you use clay strip brush on a flat surface it wont fill so fastly but if you use clay strip brush on un even surface or in holes it vigorously fills the surface which means it is failing to calculate the surfaces heights and differences.

Clearly i cannot use blender 2.82 due to this and i have not found any one using these brushes on youtube

I'm not sure if this is a regression.
In 2.80, setting Strength as 1.0 (as it is in 2.82) I had a similar result.
It is also important to note that the option Accumulate in 2.82 is enabled by default.