To me, “if you can remember your password, it is likely not strong enough“ — conflicts with suggesting it is okay for a user to use “a six-digit key code” on their iPhone.
Yes: your six-digit PIN is physically secured in ways your online passwords aren’t.
To expand on that, the iPhone hardware (secure encalve) limits the number and rate of PIN attempts. Depending on configuration, after a number of incorrect attempts, it either takes an increasingly long time to make a guess or just wipes the device (by destroying the encryption key).
This is pretty shitty advice. Online brute force attacks against passwords are rare. The only really important advice for passwords is never reuse anything. This is only achievable with a password manager. So the only really important advice is to use a password manager. Everything else is noise.
My phrasing is a way of telling people to use a password manager that doesn't rely on them understanding what "password manager" means.