I don't think beginners luck is true in that beginners win more when they first start playing but I do think beginners will win more often in tricky situations (Think poker with someone bluffing really well but a noob not realising and calling an all in) because they don't play by in a predictable or standard way.
Gambling is not a matter of luck, beginner or professional, all have same chance to winning and losing. If there are any beginners who wins it is probably one of the attraction for many more in gambling. If you don't know gambling I recommend to never gamble. Save your money to investments, savings or buying bitcoin.
I don't mean that the odds are in their favour, I just meant that because they are unpredictable in how they play they may end up winning more. I'm using poker for example, a complete newbie might get two Aces (The best starting hand) without realising how good this is. Because of this they might continue against an opponent who gets top pair of kings, as the hand progresses the opponent may go all an because of their large winning odds and the passiveness of the noob (Not betting much as they don't know how much to bet) only for the noob to win a bunch of money because they don't know "standard strategy"
This isn't a great example but I hope you can see where I am coming from.