vinegar has acetic acid, so perhaps he thinks the acid will help with sanitation.
However, yes, I suspect it would impart a flavor that I would not want around my beer.
StarSan is a commercial acid used for sanitizing after brewing - it is a NO RINSE sanitizer, used in a very dilute concentration (the bottle is some strong stuff, will stain counters!).
It is a wet-contact sanitizer, meaning you don't let it dry, you sanitize, then use what you've sanitized immediately thereafter. (bottles, buckets, tubing, etc.)
A spray bottle is very handy (and economical), to avoid making large batches.
Sanitizing takes place after cleaning. Star San will not clean efficiently.
Other sanitizers include iodophor (no rinse) and household bleach (extensive rinsing required).