FWIW the email provider of my POP3 account is Comcast in the USA (which is also known as Xfinity.)
I tried this experiment in AquaMail:
In the Inbox I deleted a message 'permanently.'
In the Deleted folder I deleted a message 'permanently.'
After allowing 5 minutes to pass, to give Aqua an opportunity to communicate with my POP3 server, I went directly to my email account online. Both messages were still present.
I agree that we need to experiment because different email servers work differently. In my case, deleting messages 'permanently' in Aqua does not remove them from the POP3 server.