There are superstitious gamblers and their beliefs are very ridiculous like what you narrated, it doesn't make sense that sharing how you placed your bet can change your luck. I guess they somehow believe that since lesser bettors wins their bets compared to multitudes that will lose and they want to be among the few. Buy sharing their bet it will increase the number of bettors that will place in the same formation and they will likely lose.
I noticed there are more superstition in lottery, some lottery players will see sets of numbers written somewhere and they will take it as a sign of winning numbers.
For sure, but i would go as far to say that most people are superstitious when it comes to gambling. They just don't realize it.
Instead of believing that results are linked to destiny, luck (as magical sense), spirits, faith, numerology, psychic predictions or something like that. They instead follow their instinct, or their feeling about the game. They might even believe that changing machines or casinos in some order would bring them more winnings, because it happened once or twice. They also might have a strategy that's based on gambler's fallacy.
I see it as similar belief, but instead of magic, it's just magical thinking that's loosely based on failing logic.