This might just be me misunderstanding what the tool was made for, but if I try and export room data using this commandline

emm -hs hs.example.org -u username -p password -r "#room:hs.example.org" -o "room-{{ .CreatedAtDate }}"

I get single files, room-2025-04-22, room-2025-04-23, containing only one message each.

If I run the same command without the CreatedAtDate template in the filename, I get a single file containing multiple messages across days.

The behaviour for using a template that spans an entire day is not mentioned specifically in the docs, so its completely on me to expect messages to be appended to an existing file, but, them not being appended kind of makes using template tokens that aren't unique for each message useless.