“Seen __ mins ago”

So this is definitely not life or death lol but I’m just confused?

On my old phone, when I would go check Facebook messenger, if someone read my message it would tell me when it happened.

Now on this new phone for some reason, it tells me way after.

For example,

This says he read it 40 mins ago but he’s just now active.

And no, I’m not worried about it or mad from a late reply lol. It just doesn’t make sense because I have been checking to see if he read it this whole time and it kept saying it was just “delivered”

But now suddenly when he’s active it shows “seen” but “seen 40 mins ago” ... so why couldn’t it show me that 40 mins ago is my question lol

Seriously I know this is so dumb but I just want to know why!

I thought “oh maybe he’s just marking it as unread until he wants to reply?” Which would be okay I don’t care, but it happens every single message and I know he’s too lazy to do that all day everyday and it happens with everyone else too