I don't know if we're quite ready to start referring to Pettis as some kind of submission artist; sure he just scored a submission victory over a truly legit guy in Bendo but it's not exactly the norm. This isn't Frank Mir we're talking about.
Charles Oliveira by comparison has a far greater reputation for submitting guys off of his back and Frankie didn't really have too much of a problem taking him down at will. Frankie is probably the last guy that would be afraid of taking someone down in fear of being submittied, he has a very legit ground game himself, and has escaped extremely dangerous positions on the ground on multiple occasions.
I think Pettis was just a bad matchup for Hendo, I think he has his number and that it's almost entirely because he has the psychological edge over him. Bendo didn't really seem himself, he came across as being afraid to stand with Pettis and tried to grind it out as much as he could. Bendo is at his best when he mixes things up but he came across as being far too tentative against Pettis and basically wanted to outwrestle him and minimising the standing exchanges as much as possible.
I also think Bendo was probably still hurt from those body kicks when they went to the ground and physically just wasn't able to stop the submission in time, it seems to be what Pettis is crediting the submission with and if you look at Bendo in previous fights he's usually far more solid and mobile in that position.
Frankie has the better footwork and boxing going into the matchup and has a number of counter measures against Pettis's most dangerous weapons in his kicks - he's got the best takedowns at that division and will probably be able to take him down every time Pettis throws one, he's pretty much the best in the business at catching kicks, and if a few land, he's basically so tough that he would in all likelihood not even be phased by them - I mean Jose Aldo's leg kicks by all accounts are some of the most powerful strikes you can be on the receiving end of and Frankie took a number of them without ever slowing his pace and changing up his footwork for the entire 5 rounds. I see him flustering Pettis with his footwork, his pace, mixing up his striking and wrestling, and making him pay every time he throws a kick - and when it gets to the ground defending against any submission attempts. Anybody can get finished but I think Frankie might be the single most unfinishable fighter in the UFC, so I see it being a clear decision for him.
Pettis's UFC run has really not been particularly impressive aside from the fight with Bendo, I mean he lost to Clay Guida, got a split decision victory over Jeremy Stephens, Joe Lauzon was never truly a very good fighter and Donald Cerrone hasn't looked all that great in his last few fights either. Frankie has been far more impressive in that same time span and has the tools to make him a bad matchup for Pettis. The fights with BJ, Gray, Bendo and Aldo were largely so competitive because he was facing guys that could give him trouble standing but were also really good wrestlers themselves (defensively in BJ and Jose's cases) - in Pettis he faces a guy with pretty mediocre wrestling.