thank you, why would Motorola do something like that?
Sabers are Reagan era technology, first hit the market in 1987. When they did, the original models didn't even have the two side buttons, they would show up around 1990 on the second revision of the product line. This coincided with the advanced Stat-Alert package, which was part of the then recent APCO-16 feature set requirement for public safety.
In those days, radios didn't use flash memory, features were 100 percent hard coded in ROM chips. Not every customer needed the advanced Stat-Alert package, as it did cost quite a bit extra. Most of the Sabers sold had less feature laden CORES (CORE is an acronym for Control of Radio Electronics BTW) but one housing and flex assembly was made, so a post-1990 5D or 6D CORE Saber will still have the two buttons, but they aren't used for anything.