But by saying, " a urethane ball will react fairly well on these conditions", they're already contradicting themselves, whoever they are. I've seen plastic roll out at the arrows on unoiled lanes, but again unless you define all factors thoroughly, like the lane surface, you're mixing terms and environments so that there are too many unknowns.
Friction provided by the environment is one operative word: that's oil + lane surface.
FRICTION provided by the ball's surface and the bowler's ball speed is the other operative word.
"None are so blind as those who will not see."