There are so many examples in this thread alone as to why this rule doesn’t work.
SCUBA: the U is for “underwater” and the A is for “apparatus”. We don’t pronounce it “SC-uh-B-ahhh”.
JPEG: The P is for “photographic”. We don’t pronounce it “JayFeg”.
LASER: The E is for “emission”. We don’t pronounce it “Lay-See-R”.
RADAR: The second A is for “And” (lol). We don’t pronounce it “Ray-Day-R”.
The easiest “rule” is just the guy who made it up can dictate how they want it spelled and to pronounce. The word is made up anyway, and isn’t subject to rules that actual English words have been subjected to for however long the language evolved.