I didn't say it was a bad idea, I said it was unnecessary, and I gave my experience dealing with students who took or were taking it.
By overthink, I mean they approach the problems as if they're harder than they actually are. They get in formal logic, and they see all kinds of symbols and formulas and other such jibberish and they want to use all of it on the LSAT. They tie themselves in knots trying to find implications and inconsistencies and whatever else because they think the LSAT supposed to resemble the messes they had to untangle in class.
All the "formal logic" you need for the LSAT are conditionals and contrapositives, which can be learned in like 30 minutes from any LSAT book or just browsing this forum. Anything beyond that is completely unnecessary.