Was looking for this comment. You articulate it well. Many people claim they "can't sing" but when they try it's clear to me they just have an underdeveloped muscle control
Some people can't tell if the note they're singing is the same as the note they just heard. This is also learnable but it's not as simple as just muscle control
I'm perfectly willing to grant that this is the usual case, but since I'm not interested enough in being able to sing well to dedicate a lot of effort to it, it doesn't matter. I probably wouldn't sing if I had the voice of an angel.
