Dovecot submission proxy constraints

[Peter Wienemann]

Dear Dovecot experts,

in 2017 Stephan Bosch mentioned in an email about the Dovecot submission 
proxy [0]:

"The current implementation does require that the proxy has direct 
access to the user's mailbox for BURL (e.g. by running it on the same 
host as imap), but that restriction should be resolved soon, allowing 
for more complex setups."

Is the mentioned restriction (access to mailbox) still valid in 2023 or 
has this constraint been lifted in the meantime?

Best regards,

Peter

[0] https://dovecot.org/pipermail/dovecot/2017-December/110282.html