I've heard the phase but can't remember the explanation. I think what you need for unknown film is indeed a compensating developer. I recommend Agfa Rodinal diluted 200:1, stand developed for two hours, 20 inversions at the start and a single inversion after an hour. Plain water stop, fix, wash...
In camera A7Riii jpg, no adjustment in post. I exposed based on the mid sky reading without adjustment. Generally for both film and digital I prefer to do only minimal adjustment to what is recorded.