Comment by microtonal

This is extremely hard to implement in a non-superficial way that would be hard to detect.

Android switched from block device encryption to filesystem-based encryption (with encryption data and metadata). This provides many security improvements, such as per-file encryption keys and per-profile keys.

However, this also means that the main file system is readable and you could enumerate the available users. If you would encrypt/obscure that information, you could still infer the presence of other profiles from file system block allocations.

(Disclaimer: not an expert, but I read the relevant Android docs at some point.)