This is really bad advice. Site like this often exist only to get your private data so active email address that you checking.
Better method is to register with new email on every new website. So for example you use:
peter@gmail.com (as personal email but you want to register on coinbase and gemini exchange)
peter_gemini@gmail.com (create filter to redirect all emails to
peter@gmail.com)
peter_coinbase@gmail.com (create filter to redirect all emails to
peter@gmail.com)
Then you use one email, but you are 100% sure from which service (email) you start to receive spam.
I imagine there are people who will setup their email password this way:
peter@gmail.com: passphrase A + (@gmail or _gmail or gmail)
peter_gemini@gmail.com: passphrase A + (@gemini or _gemini or gemini)
peter_coinbase@gmail.com: passphrase A + (@coinbase or _coinbase or coinbase)
This is a very terrible method to setup password. The better method is using randomly created passwords.