What you highlighted there sums it up well I think - ‘the most likely theory’.From what I saw of the last tranche of the inquest, a theory had been formulated around the FFC, based upon her being a suspect that couldn't be cleared. The FFC according to the evidence, has no corroborated alibi for when WT disappeared. The most likely scenario needed to be investigated.
An incident involving anyone other than those in the house that morning would require the pure chance of someone stumbling by that house in the 5-odd minutes that WT was ‘unsupervised’ - or having been waiting for such an opportunity. Of course, this MAY have happened, it just introduces a whole new lot of variables that aren’t involved if whatever occurred only involved the parties present in the house. I can see why LE focused where they did after reviewing all the ‘evidence’. There simply wasn’t enough to conclusively clear the parties of the house, and as it requires the least variables it became the focus of the new investigation.
Now that it hasn’t seemed to result - LE need to decide what the next step is. This is an investigation that has gone on for far longer than it should have, ruined careers, traumatised witnesses and other associated people, and so far failed to bring justice for WT. I’m sure we all hope this case is resolved the right way as soon as it can be, it just seems that LE aren’t any closer now than they were on day one.
Whoever the guilty party truly is has gotten away with this for far too long.