Unless you sleepwalk, or are a 'flailer' there's little risk to sleeping with an infant in bed with you.
Idea for testing it out:
get a cabbage patch doll, hard boil an egg and shell it, put the egg in a clear ziplock bag, and tape the bag to doll. Check if it's squished in the morning. You may need multiple eggs on different limbs, maybe multiple eggs per bag, to account for the full size of the doll.
The problem is you would need to repeat this experiment every day for 8 months - and even then that's not enough data for a new parent to be confident. It only needs to go wrong once remember.
You're playing the odds. Some children die because they get accidentally smothered in their parent's beds. You can either take the (very small) risk that this will happen and sleep with your child in bed, or you can just not play the game at all.
And for most, I think whilst the reward is "good", the failure is just unthinkably horrific.
Idea for testing it out:
get a cabbage patch doll, hard boil an egg and shell it, put the egg in a clear ziplock bag, and tape the bag to doll. Check if it's squished in the morning. You may need multiple eggs on different limbs, maybe multiple eggs per bag, to account for the full size of the doll.