8pm is too early?!

So my kids are 5 and 3 years old. They have a bed time routine they have both been on since they were born. They lay down at 8pm, I turn on a movie and they are out by 9pm, this happens even during the summer. My SO’s mom messages me and says she MIGHT stop by to say hi and visit (this was way earlier) she’s the type of person that says she will be “right back” but not come back till hours later.

Anyways I said ok but since it was a while ago and she didn’t confirm if she was going to or not I laid my kids down for bed at 8; 830pm rolls around and we hear a knock then she comes in, and yells “hello?”. Didn’t bother me that she walked in cause quiet frankly I don’t care if and only if it’s family, this is how our convo went...

Me: I didn’t think you were coming, the kids are in bed now

Her: I said I was

Me: no you said MIGHT but that was hella earlier it’s 830 now, it’s fine the kids are in their room they haven’t fallen a sleep yet.

She walks in the room and says “why you guys in bed so early?” I looked at my phone and was like “tf? Does she mean early it’s almost 9pm”. They love to see their grandma so I didn’t care if they stayed up to visit....

My question is: when you do think “too early” for bed time is? Also do you think 8pm is too early for a 5 and 3 year old?