My emphasis is on the word "risk" (captured in the literal words "most likely"). It's risky to go without a guide, though it's not "needed" in the sense of a 100% failure rate.
Honestly, the fact that you assumed others were talking about "have a guide or 100% failure" is disingenuous on your part.
Honestly, the fact that you assumed others were talking about "have a guide or 100% failure" is disingenuous on your part.