This must be a local habit - 10 yrs on the 737 across 3 companies and never heard such a thing. No Boeing reference to this I'm sure. (stands by to eat hat)
Bet you never thought to taxi in the dark with no taxi lights - apparently to "save the bulbs", or fail to get en-route or terminal diversion weather as it is "CAVOK down there", or prefix your callsign with "The...". or say "Fully" before ready for departure, pushback, established and a lot of other times too. Some do! Bizarre!
Some very strange ideas sometimes develop over time in the closed environment of a company's operational habits.