autopkgtest log is missing stderr output

Some time between 2 and 3 months ago, the autopkgtest test log stopped including the stderr output from autopkgtest.

I have plenty of tests that "set -x" (along with Restrictions: allow-stderr), but that output doesn't show up anymore.

I originally discovered the issue in postgis (https://salsa.debian.org/debian-gis-team/postgis/-/jobs/2805529), but digging closer into the pgpool2 logs, I can vaguely pinpoint the time where it happened:

• Bad output without stderr from "2 months ago" https://salsa.debian.org/postgresql/pgpool2/-/jobs/2549938

Removing autopkgtest-satdep (0) ...
### PostgreSQL 14 psql ###

• Good output with stderr from "3 months ago" https://salsa.debian.org/postgresql/pgpool2/-/jobs/2454919

Removing autopkgtest-satdep (0) ...
autopkgtest [04:30:19]: test installcheck: [-----------------------
+ pg_buildext psql
### PostgreSQL 14 psql ###

Note that both the set -x "+ command" and the "[-----" output from autopkgtest are missing.