Oscar doesn't lose a couple of mili seconds every corner. Almost 40% of the gap is made in T3 alone. From the onboard of Lando's lap, honestly the T3 was just perfect. The car seems to be gliding over the kerb as it is not even there. No problems with the traction out of it either. Leclerc got close, but he did so while pushing the entries. He got a wobble out of the exit (as you would expect) so ended up half a tenth behind Lando by the end of S1.
As for the rest, he has been 1.5-2 tenths weak to Lando in S2 the whole weekend, so it's not exactly surprising. Lando just completely nailed S3 on his final run and that's where the rest of the gap comes from. Zero wheelspin as far as I could see on the onboard. Maybe a tiny bit out of T16, but that was actually beneficiary since it pulled the car to point a little bit to the right and shortened the distance to the finish line.