That doesn't mean they're stupid. If you say "V" over a phone or radio, it can be hard to tell if you said V or B. Likewise with M and N, and plenty of others.

The pneumonic phonetic alphabet (the real one, not this shitpost) disambiguates the sounds so there's no confusion. People who don't know pneumonic phonetic alphabet sometimes pick a random word or name to use for the same reason, i.e. "V as in vagabond"

If you're spelling something pneumonically phonetically to someone who doesn't know the pneumonic phonetic alphabet, it can be hard for them to catch the sounds they're not used to. Especially if you don't tell them what you're doing before you start spelling, it can sound like you're just throwing random words at them.

To illustrate the point, pick a language you don't know, and ask someone who speaks that language to spell out a word in their alphabet. Or maybe find some videos online of spelling quizzes in other languages. Most of the letters probably begin with the same sounds they make. So if your theory is true, then if you aren't stupid it should be easy to catch what they're spelling. Not the case though.