Hot take: you need to trim your pad edges after cutting, not before

I worked with this old timer named Ray on a job in Amarillo about three years back, and he watched me glue down a stretch of 8 pound pad. I was cutting it to size first and then stapling it down neat. He shook his head and told me the pad has to go down bigger than the room, then get trimmed along the wall after it relaxes. I argued with him for maybe ten minutes. He said the pad will shrink back about a quarter inch once it sits, especially in that dry Texas heat. Did it his way on the next three rooms and every seam came out tight with no gaps at the baseboard. Now I trim after tacking every single time. Does anyone else cut pad before or after laying it, and which way do you go?