I've noticed that whenever a segmented control first gets rendered onto a page, its height "animates" to its final height. This is fairly ugly behavior.

Hello Ion,

This is a feature of the native iOS control. Unfortunately, there is currently no way to remove it. We do have the request in our backlog - https://feedback.telerik.com/xamarin/1406598-segmentedcontrol-ios-provide-a-way-to-remove-the-initial-animation 

If you add your vote to the item, it will increase the priority of the request. If you Follow the item, you'll be notified of status changes (Approved, In Development, etc).

Regards,
Lance | Technical Support Engineer, Principal
Progress Telerik