The tweet mentions that huge XSS payloads in POST requests did not help in bypassing Sucuri, Akamai, or Imperva WAF in preliminary tests. The technique was unsuccessful in these tests. It calls for success stories with that technique against major WAFs. The tweet signifies the difficulty in bypassing these WAFs using XSS payloads in POST requests.
For more insights, check out the original tweet here: https://twitter.com/RodoAssis/status/1854549457020338215