Well I know we all have different views on this.
Personally, I can't see any reason in Rebelo-day for wanting one, except to tick boxes on procedures to hand it all to the magistrate / prosecutor.
You don't actually need people present these days to work out forensic timelines or anything else. They'd had the keys long enough to verify a door potentially slamming. Why would you need the person in question actually there? Either it was possible or it wasn't.
They'd tried to get through the window to see if that was possible. There's no particular for the parents of a missing child having to be there while attempting to simulate that possibility.
The timeline isn't complicated to work out in terms of possibilities. They'd made a best guess of the times, according to their recollections of the sequence of events and whatever baseline time they were using.
There was no way on earth of determining why Gerry & Jez didn't see Jane, nor hear her flipflops. How do you scientifically determine what those two guys, deep in conversation actually perceived that night? I might have heard her flipflopping up, but it doesn't mean that they did. They did go back and all that came out of that was that they didn't agree on where exactly they were standing.
What I haven't personally seen is that Gerry (and Russell, from memory) mentioned that a date had been leaked to the media. If that's accurate, that would be the other leak I was trying to remember under Rebelo's watch - but I don't recall having seen it in the media, and it may have been off the record and got leaked via the media grapevine from there.