What is a tat?

“Tat” means miscellaneous junk.

That said, the anecdote is made up or important details have been elided to make it sound more interesting than it is. Amazon doesn’t depend on whatsapp for 2fa. You can configure amazon 2fa to send an SMS and it’s possible that the poster’s mother has misconfigured her phone to claim that it needs whatsapp to read the sms 2fa message but I highly doubt even that. When I look on amazon it allows passkeys, regular TOTP like with DUO authenticator or google authenticator or whatever or SMS with a backup of sending the TOTP code to the registered email on the account. Whatsapp isn’t even an option.

Perhaps the options vary by region?

How does "tat" differ from "grot"?

tat n.

  anything that looks cheap, is of low quality, or in bad condition:
  * Like most souvenir shops, it sells a lot of old tat.
  * I'm not spending fifty quid on a piece of tat.
People buy it all the time when they practice retail therapy.