[yellowapple]

I mean, if the point of the API is to access the filesystem, and you instead redirect those calls to a different in-memory scratch filesystem local to that incognito session and/or tab, then I'd call that shimming to at least some extent; it'd just be an especially thick shim.

[breakingcups]

In that case it might still be detectable by measuring timing of storage and retrieval?

[yellowapple]

Maybe. Adding a delay could further mask that.