I have always assumed that the film manufacturer would want a customer trying one of their films for the first time to get good, or at least acceptable, results and that I would not go too far wrong by following their exposure and development recommendations for the first few rolls at least.
(Stop bath, fixer and washing are another matter. My personal workflow has been successful for me for many years. If it doesn't work with a particular film that's the end of that film for me.)
Besides which, the differences in ISO being discussed are seldom more than one full stop, which is within the margin of error most metering (Zone System acolytes with proper spot meters excepted

.