As we both know that it would have been difficult to switch on the medium tyres for both Ferrari's in just 1 lap, they were sent out to do 2-3 fast laps.
On top of that Vettel was stuck behind a Toro Rosso till S2 which compromised his warm up lap, the commentators did mention that some parts of the track had lower track temp due to shade which I believe would have made it even more difficult to get the tyres upto temperature after he passed the Toro Rosso, which is why Vettel didn't go all out on his first run probably because he didn't want to end up crashing knowing his tyre temp is not optimum.
Leclerc on the other hand thought his tyres were probably in the right temp on his second run so he took the risk, locked his front wheels and ended up in the barrier which ruined Vettel's second run too, so we really don't know if Vettel had more pace up his sleeve or not.
Leclerc though was 2 tenths up on Vettel in S1 on his second run and I'm sure Vettel could do similar times but is it worth to push that hard in Q2 and start the race with flat spotted tyres when you know an average lap is more than enough to guarantee a spot in Q3?