@Nukrux still, it feels like anyone with enough skill or intelligence would think "I should try that skill too" ... But okay, let's pretend we don't know this or even better, think of the MC as a genius, no OP skill just super adaptive, then it makes sense. Because when he tried the double edged cut he did it like in the third try and then he dared to say "I trained more than usual" (.......) so yeah, no way he's only someone who tries really hard, he's a prodigy........... or the manga is just not serious enough.
@Vlox And he knows all the skills of sword, so ... Is an easy guess xP
Also I don't blame the other guys for running, why? come on, they basically say that this needs a raid organized by the guild, beside, what's gonna happen if they try? they kill 3 or 5 and then they get their skull crushed and then the orcs kill the others, no one would give away his life for strangers just like that knowing very well they'll all die anyway.