@phneutre Hi, yes this is the right place for everything - even for reporting possible bugs or issues 😉
However I just tried it and it works as expected. The sync will be scheduled immideately after you either change the value or remove the value. As long as the orange bar moving around above your calendar list the sync is running. When removing the value so that the “Past time event limit” option is empty you need to give the sync some time to complete, because it then needs to sync your all your events of all calendars - that can be a lot of data and the device needs to process it, too.