Not the original guy but deception is a necessary part of martial arts and all fighters practice it to some extent. For example there are certain kicks that the

Not the original guy but deception is a necessary part of martial arts and all fighters practice it to some extent. For example there are certain kicks that the start of them looks pretty much the same so you can try tricking your opponent into thinking you are doing a push kick but then transition into something like a roundhouse. Overall they don't do stuff like cross their arms because to do anything you would need to uncross your arms, which could telegraph the attack or make it slower in many cases. As an aside I was always taught that if someone looked like they were trying to start something that I should stand with my arms extended with both palms out (like I was trying to mime the word stop to them) as it displays the intention to not fight while still keeping my hands ready to punch or throw