Hi Michael,
Thank you for contacting Syncfusion support.
#Regarding VisibleDatesChanged triggered even if the schedule is not visisble
We have found and fixed the reported scenario form our end. we will include the issue fix in our upcoming 2021 volume 2 SP which is planned to roll out on Mid of August, 2021. We appreciate your patience until then.
Regards,
SaiGanesh Sakthivel