Indeed. This discussion illustrates what's so unexpectedly weird about this: that it is not at all obvious what happened in the apartment. The obvious thing would be in through the unsecured patio door, close it behind you; open the front door; pick up child; exit carrying child; close door behind you. The latter (while carrying a child) is doable, I've done it many times when moving my own little 'uns between cars and houses at that age.
Do all that and from the outside there's going to be no sign of anything amiss; and indeed none from the inside either unless someone actually walks into the bedroom. You'll get an hour's start, and at no point are you doing anything that would look suspicious, such as climbing out of a window carrying a child.
Instead we have this odd business of a window being needlessly opened; or it never was and KM just said it was; or someone else, not the perp, opened it after GM's last visit.
Eh?