Should rolpassword be toastable?

Hello hackers,

When playing with oversized tuples, I've found that it's possible to set
such oversized password for a user, that could not be validated.
For example:
SELECT format('CREATE ROLE test_user LOGIN PASSWORD ''SCRAM-SHA-256$' || repeat('0', 2000000) || 

'4096:NuDacwYSUxeOeFUEf3ivTQ==$Wgvq3OCYrJI6eUfvKlAzn4p/j3mzgWzXbVnWeFK1qhY=:r1qSP0j2QojCjLpFUjI0i6ckInvxJDKoyWnN3zF8WCM='';')
\gexec
-- the password is "pass"
(One can achieve the same result with a large salt size, for example, 2048.)

psql -U "test_user" -c "SELECT 1"
psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: FATAL:  cannot read pg_class without having 
selected a database

I've tried to set attstorage = 'p' for the rolpassword attribute forcefully
by dirty hacking genbki.pl, and as a result I get an error on CREATE ROLE:
ERROR:  row is too big: size 2000256, maximum size 8160

Best regards,
Alexander