Very similar heuristic here, insofar as when to use passphrases and how long.

LUKS and Bitlocker volumes get 8 words, computer logins usually get 4 words (potentially more depending on frequency/criticality of system).

Smartcards and mobile devices do have numeric pins due to frequency of use and relative difficulty in copying those for offline attacks.

Websites that are filled in w/ password manager get passwords get the random symbol-laden strings that ‘meet requirements’