When I was a teenager I had a Japanese major-brand motorscooter with a grease nipple on the front hub. When I greased it, one of the oil seals blew out. Very annoying.
It is possible to fit one of the deck-spindle oil seals (top or bottom) backwards so the lip will lift when there is grease pressure behind it, or just rely on some form of labyrinth seal instead of an oil seal. I've seen both methods used, though not on mowers. Mowers are IMO not a good place for half-engineered sealing, because the dust and grass get into everything given the slightest chance.
