That's one option to have plausible deniability (if done right) with a sacrificial wallet for an empty mnemonic passphrase, while your main wallet(s) are hidden behind complex strong different mnemonic passphrase(s). Of course, you can't store a physical backup of your mnemonic passphrase any near your wallet or its mnemonic recovery words. Good separation is key here.

Another important option is to hide your main wallet should your separate storage location of your physical backup of your recovery words become compromised. The sacrificial wallet with the empty mnemonic passphrase could act as a canary when it's emptied by a thief.

I don't recommend to try to memorize your optional mnemonic passphrase(s). Sooner or later your memory will fail you and you'll be screwed if your wet memory was your only backup. Always have one or more physical (non-digital) backups, completely separate from your wallet's mnemonic recovery words.