Quite the opposite, in fact -- if you say тугой figuratively about a person, it means a "slow thinker".
This is something new in Russian.

"Тугой" can be applied to a process and it means that process is going slowly and needs essential efforts to go on ("дело идет туго"). There is word тугодум (from туго + думать) which indeed means "slow thinker" but the word тугой by itself is not applicable to a person (unless it is some kind of rare slang).

There is also a word of the same root, which you can find interesting - "тужиться".

And BTW I never met a phrase "тугое мясо". Usually they say "жесткое мясо". If I'd hear "тугое мясо" without context I can guess that it is a street slang containing a compliment about some female shapes.