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(dot)inform(at)pharmapp(dot)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