Correct. If a start time is missed (say due to shutdown) it is not noticed at power on and the next backup won’t occur until the next scheduled time. Note that this can also happen if the Duplicati server (whether as tray icon or a service) is not running / stopped. So if you are running Duplicati SOLELY via Tray Icon and turn your computer on but don’t log in (thus starting the tray icon), no backups will run.
Note that if the service is not actually stopped (for example the computer was just asleep during scheduled run time) then on wakeup Duplicati WILL notice the missed event and go ahead and run the backup. (This is what happens on my laptop all the time.)
Personally I’d like a setting to allow Duplicati to start a “missed” backup event if the last run time is OLDER than the last scheduled time. This would help in scenarios that are the inverse of yours such as weekly backups where missing a scheduled backup start time due to being powered down means no backup for up to another whole week!
As far as scheduling hourly backups, that would help get around the current functionality. Note that by default Duplicati doesn’t save an actual backup if no files have been changed, so it’s not like you should be getting 24 backups every single day (unless you’re including temp files and the like).
If you do go this route, you might also want to look at the --retention-policy feature that was added to one of the more recent canary versions. It basically lets you “thin out” versions as they get older - for example, you could say you only want to keep your hourly backups for a day (resulting 1 daily backup for anything older than a 1 day) then set daily backups to be kept only for a week (resulting in 4 weekly backups for a month), etc.