A lot of so-called "rules" were local only.
The white shirt only rule. I remembered that being a rule in one congregation, but in another congregation in the same city, there was no such rule.
The same with denim skirts. Some places it was not an issue, others it was grieving the holy spirit to wear such a garment.
One congregation required a suit for giving the Sunday talk and doing the WT study, but the other meetings, slacks and sport jacket were okay. Other congregations required a suit for any part from the platform.
Depending on how conservative the body of elders was determined how strict a lot of these "rules" were.
It was tough moving from a fairly liberal congregation to a conservative one where a lot of the things taken for granted previously were now "wrong".
Grooming laws I was counseled on over time...
The army jacket as I mentioned before
Rock concert T-shirts
Loud, colorful neckties
Hair too long, mustache too long
Not wearing a jacket (suit, sport or otherwise) in service
Not wearing a proper overcoat in service during the winter (waist length jackets were not allowed. They had to be 3/4 or full length overcoats)
These rules are for a couple of reasons:
One, they want to protect the "christian, conservative" reputation. Don't do anything that brings attention to yourself or trumps your message or work as a magazine peddler.
Two, it's a control issue. If you willingly, uncomplainingly follow arbitrary rules on every little thing from the color of your tie to the fabric of your skirt to how clean your shoes are, then odds are you'll obey in most any other matter. If you flinch at the counsel or resist changing to adhere to the code, then it sends a signal to the elders that you aren't fully with the program. They'll keep an eye on you and try to work to get you in line.