Do cases for iPad 10.2 fit iPad Air 10.5?

No. Fitted cases designed for the 10.2” iPad7 will not fit an iPad Pro 10.5”. Their physical dimensions differ.

However, some cases intended for the current third-generation iPad Air are compatible with the iPad Pro 10.5” - and vice versa. The Air3 is largely based on the iPad Pro 10.5”, but lacks two of the four speakers found on the Pro. You would need to verify that a specific case is compatible.

There are cases that both fit the 2019, 10.2 inch screen 7th gen iPad and the 2019 10.5 inch iPad Air 3.

The external size dimensions are practically identical.

Only the screen size gets bigger and the outer screen bezels get narrower.

The 10.2 inch screen iPad 7th gen are the same external dimensions as the 10.5 inch screen iPad Air.

Here's an examples of a case that fits both.

https://www.logitech.com/en-us/product/combo-touch.html?crid=1762