Broody runners?

[EeyoreD]

How rare is it for them to nest and brood? I was led to believe they were pure layers and they wouldn't lay in one spot but just drop them as they felt like. But 2 of my three females hid their eggs and are now sitting them. I think my third female is also hiding but she's not nesting. From my understanding that would be as weird as an ISA Brown deciding she wanted to hatch.

Or am I wrong about runners (obviously they're individuals but generally, they don't go broody, right? Or are not supposed to?)

 

[TLWR]

Of my original 3, 1 was trying to be broody for a few days. Another sat for like a day.
They lay in the duck house, though after the early morning lay, if somebody didn't and needs to, it is in the pond, yard or where ever they happen to be. That's typically Ally that does that.

Every now and then I find buried eggs in the duck house. This morning 3 were visible and 1 buried. 1 missing. The buried one was either Ally's (highly unlikely) or Attu's (WH).