That is basically all this study is showing. The NFL (American football) used to subscribe to this and had strict rules over what numbers people could wear. 1-19 were reserved for the smallest players (quarterbacks, punters, and kickers). That was loosened roughly 25 years ago to allow slightly bigger players (wide receivers). They loosened it even more drastically within the last few years to allow most players to wear 0-19. It therefore isn't a surprise that people who see small numbers have a bias to think that player is smaller as that has been historically true. It would be interesting to repeat this study among younger generations of Americans and then international people who have no knowledge of the NFL. I would expect the first group would have a weaker effect and it might disappear entirely for the second group.
*Number ranges used to be used to indicate a player position, not their size... The average quarterback is significantly larger than the average cornerback, for example, and punters or kickers have no typical size (body size/shape doesn't factor into kicking ability).
