That is exactly backwards - ale yeasts are so-called "top-fermenting", prefer higher temperatures, and typically finish faster. Also, there is typically no oxygen available during fermentation beyond what is dissolved in the wort to begin with. Any oxygen in the fermenter's headspace is quickly pushed out by the yeast's CO2 production. The dissolved oxygen is quickly consumed by the yeast.
That said, I believe many breweries have figured out rapid lager production processes and are able to turn around lagers in about the same time as ales.
That said, I believe many breweries have figured out rapid lager production processes and are able to turn around lagers in about the same time as ales.