DDU - why is it important?

[Parisien_entraide]

What Nvidia advises is to empty the shaders' cache:

- During a graphics card change (same brand but different model) (1)
- During a major pilot version (branch) version or in case of problems (crash games) during a conventional update (2)


(1)But if we change brand (NVIDIA ---> AMD or Intel and vice versa) you must use DDU
(2) And, even if this does not pose any problems "in general", in the documentation of Nvidia for the pilots it is indicated clearly that one should never use a restoration point to put the old pilots for example...

[masonparker]

What specific issues or problems might arise if one does not empty the shaders' cache during a graphics card change or a major driver update, as advised by Nvidia?