BUG #17387: Working in PG13 but not in PGH14: array_agg(RECORD)

The following bug has been logged on the website:

Bug reference:      17387
Logged by:          James Inform
Email address:      james.inform@pharmapp.de
PostgreSQL version: 14.1
Operating system:   Mac and Linux (Ubuntu)
Description:

While the following sql works under PG13:

with q_data as (
  select '1' as testa, 1 as testb 
  union
  select '2' as testa, 2 as testb 
  union
  select '3' as testa, 3 as testb 
  union
  select '4' as testa, 4 as testb 
)
select array_agg(q) || array_agg(q) from q_data q;

and results in:
 {"(3,3)","(1,1)","(4,4)","(2,2)","(3,3)","(1,1)","(4,4)","(2,2)"}

the same SQL on PG14.1 fails with:

ERROR:  operator is not unique: record[] || record[]
LINE 10: select array_agg(q) || array_agg(q) from q_data q;
                                               ^
HINT:  Could not choose a best candidate operator. You might need to add
explicit type casts.

Let's not discuss if such an sql makes sense.
But question is: Why is PG14 giving an error while PG13 works?

Cheers,
James