slightly unexpected result

imagine a simple table with 1 row

=# table tf;
 i | x  
---+----
 1 | xx
(1 row)

And this query:

with x as (update tf set i=i+1 returning *)

, y as (update tf set x=x||'yy' returning *)

select * from x,y;

My PG14 gives this result

 i | x | i | x
---+---+---+---
(0 rows)

To me that was a bit surprising. I would have expected it to fail with something like "can't update the same row twice in the same command".

If I check the table content after the query I see the i=i+1 part was executed.

Is this expected behavior?

Thanks,

Torsten