Sil 9yo sprayed poop on bathroom walls?

​I have my sister in laws kids over

One is 9 and the other is 7

The 9yo got up earlier in the morning and must have had a bad stomach. I went to the bathroom early and saw he had basically 'missed' spraying his poop over the toilet, walls and floor. he must have got most of it in but I found it on the handle the sink walls and floor. ​

I was surprised and just cleaned it before everyone else was up to save any of his embarrassment. I told my wife only who basically amounted to "all well boys be boys" but I'm kinda shocked that a 9yo would do that.

I understand kids sometimes have accidents but I don't even think he told his mum? Just kinda sprayed and left lmao

I really don't mind but should a 9yo do that at that age? If my kid that I would be horrified tbh. And I don't remember doing that as a child even younger than that but maybe I did and its normal to sometimes happen?

I only ask as I'm a pretty new dad myself so I'm trying to figure out what's 'normal' for kids and I feel like an asshole for thinking a child shouldn't do that at that age.. I also want to figure out if my wife should have had a stronger reaction to it.

Side note that they spoil them quite a bit and there are just some behaviours I'm a bit surprised by from them. Like the other day he called his mum by his name telling us "sister in laws name wants you to take this". I gently asked him do you mean mum not her actual name and he kinda shrugged it off. Again my wife was like 'haha how could he say her name.."

My mum would have sent my head through a wall if I called her by her name in front of company.

There is so many other things he does and examples I could give where I end up just thinking wow he's a little rude and her family don't really discipline him like visibly​ they do these little no I said so etc but these bigger things i hardly see it. It makes me not like him so much. And I hate to say it because he's a child but I find him just kinda spoiled and naughty. Obsessed with food as all kids are but he says to his mom "wheres dinner thats your job" and things of that nature. He's a good kid. Not bad just spoiled

They watch wayyy to much YouTube, ​. But that's just my opinion.

Anyways poop. Am I wrong for thinking that's just not normal? my wife brushed it off but I don't think its that minor. we have a 1yo and now we have a grubby toilet I can't clean until they leave properly while everyone is using it and possibly getting poop around the house in micro particles on hands light switches. not hyginic for a 1yo. what can be done as its done now but yeah.. Is this ok or normal?​