Again, the link you have shared, while informative, speaks only to the security of the vault in the cloud and during transfer to/from the cloud. I does not address anything that happens on the user’s computer when the local vault copy is locked or unlocked.
The vault (and/or the stored decryption key) can certainly be copied and transferred to a threat actor (example).
Once a copy of the data is in the attacker’s possession, they don’t have to use the Bitwarden apps to do the decryption. The algorithms are open source, so there is nothing to stop a hacker from reproducing the decryption algorithms minus the part where the PIN is reset after 5 attempts.
Depending on how the vault decryption key has been protected, it may be as simple as using a third-party tool like Hashcat or John the Ripper to crack it (and then use it to unlock the vault).
I think the easiest way to get to the answer I am looking for, is to clarify whether or not using a locally stored, encrypted Excel file to store passwords would be any less safe a solution than using Bitwarden. I would hope that Bitwarden would represent a more secure solution, but so far I have not seen any evidence of this.