They worded it poorly, as the seas are methane, which is not oil - on earth it's the prime component of natural gas, so the better term would simply be "hydrocarbons". That said, hydrocarbons do not need life to form - just hydrogen, carbon, and a shortage of any oxidizers that could break them down into the lower energy states of H2O and CO2. Even longer chain hydrocarbons can form naturally - on Titan, that happens in the upper atmosphere by photochemical reactions.
It's important not to overgeneralize Earth to other celestial bodies. For example, you can even have bodies with oxygen atmospheres without life. We see this (to a tiny extent) on Europa, which has an extremely thin oxygen atmosphere from photolysis of water ice. It's quite possible that in other systems there could be an environment that produces a denser O2 atmosphere through a similar process - or through other processes, both known or not yet conceived of.
The universe is a weird place. Think about what a tidally locked rocky planet orbiting close to its parent star would experience. I read about one planet whose night side temperature was expected to be earthlike but with a hot side temperature of thousands of degrees. So think about it for a second, what's going to happen? The hot side is going to constantly boil off, potentially even to plasma, be circulated around to the cold side, and then rain down rock. Rockstorms. Depending on the properties of the rock, the rate of boil-off, the rate of redistribution, and the properties of the atmosphere, it could be anywhere from dust to large chunks, and anything from volcanic-like ash to pele's hair (rock wool) to breccias to gemstones. Lightning would be tremendous, like in some volcanic eruptions. Given the amount of energy at hand, winds in storms could get up to ridiculous intensities. The redistribution of mass is going to cause a continual planetary slump from the cold side to the hot side, so one would expect frequent, super-intense earthquakes and frequent volcanic eruptions. You might get some intense magnetic effects via an exceptionally strong dynamo effect, plus the star's magnetic field itself would be orders of magnitude stronger. Aurora could be intense enough to light the sky on the cold side and power photosynthesis. Aurora could be intense enough to light the sky and power photosynthesis on the cold side. Liquid water would be stable in certain places (if it managed not to be all blown off over geological timescales, that is, the planet would have to be large), but would be thrashed about to biblical extends by the other aforementioned processes. If the magnetic fields are strong enough, flowing saltwater may even be visibly dragged by Lorentz forces and build up charges when constrained. The dissociation of the rock on the hot side would free up oxygen into the atmosphere, which would not be all immediately consumed on the cold side (some oxidation reactions are slow). And on and on. So it's potentially possible to have livable, breathable planet with a soil made from regular rains of rock wool and gemstones, lit by aurorae and in a constantly undergoing one catastrophe after the next.