Nah, you're not being paranoid. He probably does it that way because the quicker it's done, the quicker he can have smoko, or get onto the next job. You're just worrying about the safety of your car, which you paid for, and not the mechanic. Next time, do the oil yourself, let it drain in when you put the first lot in, let it settle, turn on the engine and let it idle until the oil pressure light goes out... then turn it off, top up and then go for a 10 minute drive.