Mac Mail Send Later functionality on Ventura does not work with IMAP

Why does the email stay in the "Send Later" mailbox after it's sent, and does not appear in the regular "Sent Mail" folder like all other sent emails? We tested this several times with the same result, recipient confirmed receipt of the email but it stays in the "Send Later" folder on the local device with no indication in the "Sent Mail" folder that the email went out - this is really problematic with IMAP accounts where you're counting on all devices staying synced. Use case: I schedule an email to a client for "Send Later" on my mac that I leave in the office turned on and connected to the internet, then I want to check my iPhone later to confirm the email was sent out. This is not possible with the way "Send Later" appears to work. Also, if the client replies back, this reply is in no way connected to the original email I sent via conversation or highlighted threads.