If you configure a TextArea to be resizable, it simply is not.

https://docs.telerik.com/kendo-ui/api/javascript/ui/textarea/configuration/resize

This last worked in 2023 R1(2023.1.117): https://dojo.telerik.com/@Stephen/IqePaHim

And is first broken in 2023 R1 SP1(2023.1.314): https://dojo.telerik.com/@Stephen/UWUpoxUw

And is still broken in 2023 R1 SP2(2023.1.425): https://dojo.telerik.com/@Stephen/OnoKiboM

Notice that the resize handle is not even rendered anymore.