He's right, and a genius.
there's almost nothing you can't do with a push up to be effective.
Try this and see how well it works for you.
Try doing 4 sets every day. Spaced throughout the day.
Weighted push ups- backpack full of weights
& between chairs with your feet elevated up on a table.
If you want the best exercise for the chest. I have it. It's a variation of a slide push up.
I do mine with a weighted back pack & use dumbbells to roll or "slide" with
This is an upside down fly, and using both the pressing and fly movements at once. Its an extremely heavy inverted fly. There is no better exercise for hypertrophy than this one.
Naysayers take a hike.