Very helpful thank you for the additional insight - I'd never checked into pg_stats and that does reveal a difference in the distribution of the validation_status_code between qa and production:
prod:
│ most_common_vals │ {P,F} │
│ most_common_freqs │ {0.925967,0.000933333} │
│ histogram_bounds │ ❏ │
│ correlation │ 0.995533 │
qa:
│ most_common_vals │ {P} │
│ most_common_freqs │ {0.861633} │
│ histogram_bounds │ ❏ │
│ correlation │ 0.999961 │
so the way I am reading this is that there is likely no sensible way to avoid postgres thinking it will just have to scan the whole table because of these statistics. I can force it by setting session parameters for this particular query but I probably shouldnt be looking at system settings to brutally force random fetches.
thanks again for the assistance!