xauusd prices move faster than most conventional instruments so the beginners must be looking for a higher reward for their risk. While currency pairs like eurusd move around 100 pips in a day, xauusd can ove 200 pips in a day, making it more profitable and more risky at the same time.
I think beginners should avoid xauusd till they are sufficiently grounded in risk management and can develop a good strategy for xauusd.
When they say 90% of retail forex traders lose money, it is partly because of this kind of high risk trading by beginners who want a quick buck.
You might get lucky with xauusd a couple of times but your luck will eventually run out and if you dont know what you are doing you could make big losses and even quit trading.