Not sure how many planets have to be aligned for this to happen. The valve of my 1999 XK8 snapped when it dropped its seat, pushed itself a new hole and held ltself and the seat out of harms way. l even found the little plug of aluminum it pushed out in the head!

 

I'm running a 2002 AJ28 (S-Type 4.0) block that dropped a seat and bent the valve.
I installed a replacement engine in the customer car and saved the block.

I found a 2000 X308 LWB that had a bad engine (seized) so I pulled the heads and swapped the AJ27 heads (and oil pan) to the AJ28 block.
The wife is still driving it a few years later.

Somebody needed a bank 1 AJ28 cylinder head so I sold it.
Find a good-used AJ27 head and go on with your life!!!