Most 8 year old boys don't poop the bed unless they have some medical condition or they have diarrhea.
My own 8 year old son has pooped the bed before because of diarrhea and so when he's sick with diarrhea I have him wear diapers for it.
It's actually better for a kid and even teen and adult to wear a diaper when they have diarrhea or are sick so the diaper can catch the poop.
Sometimes I will also wear an adult diaper when I have stomach cramps and diarrhea and need to go somewhere and cannot stay home.
It's much better to have the diaper contain the poop or diarrhea than to have to run to the toilet and hope you make it.
I've had diarrhea and could not make it to the toilet and shit my pants and so it got all over my pants and was very noticeable.
But with a diaper you cannot tell that you've shit your pants and can clean it up easier.
My kids wear a disposable diaper when they are sick or have diarrhea to prevent it from getting on their clothing and bed etc.
Or if they are feeling sick such as with the flu and don't feel like getting out of bed to poop or pee they can just use the diaper and I'll change the diaper.