Re Q1, I don’t know but I had always assumed it was the easiest & cheapest way to remove the gauges. It also keeps the lightplates interchangeable between the different series of 737.
There is a precedent for this, have you noticed the caption sized gap between the two RAM DOOR FULL OPEN lights on the pneumatics panel? This was the * ******* ****** light on the 1/200 series. They didn’t close the gap when the light was removed. I will leave it as a quiz for you to remember or find out what the caption said.
Regards
S&L