I use my iPad with a keyboard a lot for writing but I think Apple has made a mistake with IOS 9.

I used to be able to shift-option-arrow to select words from a start point to wherever I place the cursor. But now when I press shift-option-left it expands the selection left and when I press shift-option-right it expands it to the right.

I can no longer reduce the selection using the keyboard. It only expands.

It should work just like on my Mac. Why change this?

This is a bad decision. It's affecting Evernote, Day One. But strangely is not affecting the Google search box in Safari.

I feel frustrated now when I try to edit text and I have downgraded to IOS 8 so that the device is usable for my main use case.

It shouldn't be like this. If you're frustrated by this as well or have an idea on how to revert the behavior, please add your voice to the Apple Support Forum discussion I created.