Why does an ack‑based cron job fail after applying CIS Benchmarks on AlmaLinux 8?

After hardening an AlmaLinux 8 system with the CIS Security Benchmarks, a cron job that uses ack to search a log file returns zero matches, while the same command works correctly when run from an interactive shell. This causes monitoring or alerting scripts to fail. What explains this discrepancy, and how can the cron job be fixed while remaining compliant with the benchmark?