My uncle ran a cabinet shop in Kalamazoo for like 30 years and he told me the same thing about leaving drawers loose. Turns out he was just building them to fit the cheap wooden runners he made himself from scrap, so yeah the 1/16" was for his setup, not some universal rule. I read a thing on a woodworking forum where a guy measured a bunch of old dressers and most of the good ones were closer to 1/32" with metal slides. The wood movement argument only really matters if you're running wood on wood, and even then it's the sides that move, not the width of the drawer. Your old boss basically gave you a number that worked for his cheap method and dressed it up as wisdom. Four years is a long time to run with bad advice though, that stings.

That lines up with what I ran into when I stopped treating salt like it was the only thing keeping mold away. I did a similar test with a few jars of carrots and beets, kept one at 3 percent and one closer to 2, and the lower one stayed crunchy while the salty one went soft on me. The thing that finally clicked was that the salt is mostly there to hold things steady for the first few days until the acid builds up, then the pH takes over and does the heavy lifting. Now I check the veggies and how much water they're letting go before I pick a number, and I keep the jars a bit cooler so things move slower. It's less of a set rule for me now and more of a feel for the batch.