I'm a hobby CNC'er so don't use complex programs but I always start my programs with a G80 in the first line, I used to teach CNC programming in the 1990 which again was very basic but insisted all my students started their programs with the first line with G0 (G21 or G20) G49 G17 G80 G40 G50 G90 probably over cooked instructions and things have moved on, but when dealing with students it saved lots of crashes and damage.
Hope this helps.
Jim