For passphrases is there really a difference between a long phrase that is easy to remember with some uppercase letters vs. random words chosen from the dictionary?

A passphrase of 12 lowercase letters would require in the worst case scenario 48,000,000,000,000,000 guesses before the correct one is found.

Source: https://blog.trezor.io/is-your-passphrase-strong-enough-d687f44c63af

if that's accurate then what does it matter if these 12 chars are a memorable phrase or a few words from the dictionary in terms of security?