He is imposing a penalty to the die rolls if you act in a manner HE thinks is inconsistent with your stats.
It's not the Ref trying to role-play the character. It's the ref making sure that the stats actually mean something and aren't just window dressing.
Now, if during character generation, the player established that his baron was actually a blackguard who'd lower himself to picking pockets or picking his nose in public or stealing children's underwear from drying-lines, and habitually did so, I might waive his penalty there... and have his reputation suffer in his social circles accordingly. TANSTAAFL. He might be a baron, but his class won't really look at him that way.
I'm not saying your noble can't stoop to trying to pick the odd pocket. But if he hasn't been doing it his whole life - and it's not likely he would be - he's not going to be very good at it. It just makes SENSE.
***
There's a philosophical shift in RPGs which occurred in the 90s, mainly, which has kept me from buying any modern games.
With the games of the late 70s and early 80s, you roll your dice, and you get your stats. That's your character: you have to try to play THAT character. You got a weakling with smarts? You don't go playing him like the incredible hulk. You got a moron with muscles? That ain't Stephen Bloody Hawking walking there with the Warhammer using a Volkswagen for a shield. Come the 90s, with point-buy and so on, you pretty much get to pick your character and min-max them to your heart's desire. And can I ever tell you how much that bores me.
CT's among the oldest of the old school. You play the character how it rolls up. If your character doesn't have a skill, and tries to use it, there are negative mods, and nobody complains: it is what it is.
If there's a skill that doesn't exist, the REF can make it up, or make up rules to adjudicate it - that make SENSE. And it makes sense that a street kid with no SOC is going to have a better shot at having picked up the street skills to fish a wallet if he needs to. The second son of the first lord of the Sector Admiralty isn't going to have that ability any more than the street kid is going to know which fork to pick up for the third of seven courses of a gala dinner.