Okay, so up until a few months ago, the reason he didn't run **at pace** with the ball close to his feet at Barça is "because he was not yet confident?" That makes absolutely no sense. Carrying the ball close to your feet is **less** risky. So why would he suddenly lack confidence to execute such a skill?
This is **not** about close control brush-overs ballhandling from a dead stop, the kind of tricks he's always shown skill at. He showed up at Barça a rather sloppy technical player, by La Liga/Barça standards- the abilities to dribble and pass in tight spaces while keeping control of the ball rather than pushing and chasing it. He's tightened up his control a **lot** over the past few months.
Herpyderpy ymmv kthxbye
He barely tried to slice defenses with his runnings, always stopping the ball close to sideline and trying passes instead, "slowing build up plays" like you said a plenty of times.
This is lack of confidence.
When he tried, he failed because he was rusty in that matter.
That's how lack of confidence can influence something you think is purely skills.
Again: don't fool yourself, he learned it way before Barça and I myself watched it too many times to count.