Why isn't the split keyboard available on the iPad Pro 2021 (11")? This really was a great feature!

For reasons known only to the Apple Developers, the on-screen Split Keyboard is not supported by any iPad with a screen size greater than 10.5”.

As such, all 11” and 12.9” models of iPad Pro - and fourth generation 10.9” or later models of iPad Air - do not support the Split Keyboard. Instead, these models support the new Floating Keyboard in addition to the standard Full-size on-screen keyboard.

Use the floating keyboard on your iPad – Apple Support

Split and move the keyboard on your iPad – Apple Support

Apple do invite submission of comments and feature requests via its Product Feedback portal. For iPad and iPadOS:

Feedback - iPad - Apple

maybe they felt with the bigger screens it was not necessary

you can attempt to change their minds using their feedback channel

Feedback - iPad - Apple