Yes it's the actual reason. https://en.wikipedia.org/wiki/Uniform_number_(American_football)#:~:text=Certain%20numbers%20may%20only%20be,the%20officials%20in%20determining%20penalties.
"Certain numbers may only be worn by players in specific positions, thus assisting the officials in determining penalties."
"Players who wear numbers from 50 to 79 are, by rule, prohibited from catching or touching forward passes if their team is in possession of the ball and may not line up in a position that allows them to do so, unless explicitly indicated to the referee during a tackle-eligible play."