I have Empty Trash set.

I don't understand what that means. In any case, you'll need to empty the Trash after deleting messages. Use webmail if your Trash folder in Thunderbird is not identical with the Trash folder on the server. See https://support.google.com/mail/answer/78755

Empty Trash is a server setting on Exit for the account. I am not manually deleting. Thunderbird is auto-deleting items over 400 days, yet they remain on Google and get reloaded every time I start Thunderbird. All my folders are identical so that is not the issue. If I manually delete, then Google deletes, but if Thunderbird deletes, Google retains the message. I read the support article you forwarded and it's telling me the option is useless because I have to manually delete in order for Google to delete. If I have to manually delete the messages, why have this option? All other folders are displaying messages under 400 days. That doesn't mean they are deleted. All Mail is still sowing them meaning Google hasn't deleted them. If I compact, they disappear from the view but reappear when I restart Thunderbird.

It doesn't matter whether you delete messages manually or have Thunderbird delete them after 400 days. The point is that you'll need to empty the Trash. This is a Gmail feature and not a Thunderbird problem. You may address any complains to Google.