Q:

Is Blender 2.8 Cryptomatte samples dependent? 

In other words, while rendering a single 2000 sample OpenEXR Multilayer image, I open another instance of Blender, with no scene and a clean compositor.  After that I drag and drop a low sample image previously done of the same render, with the same Cryptomatte pass in it. 
Possibly I can start compositing and export the crypto-matte from here, applying it to the 2000 sample image after it finishes.  Is it right?  I see the edge of the matte untouched, as Cryptomatte works with object mesh, maintaining the luma black and white matte clean (as an object buffer, I think). 
I don't know if I'm explaining it right, but I think that the title is quite clear. 

A:

Crypto matte seems sample dependent, but I successfully use a matte generated from a low sample render scene: I than re-render in high resolution this scene using the same matte previously picked, without noise or artifacts.