I have pondered the same. There was no visual verification of W after his prominent display on FD's shoulders captured on McD's CCTV (other than by members of the foster family). Five photos of W all taken quickly in a row of nothing particularly special, was the proof of life at Benaroon Drive the morning of his disappearance - up until it came into question during the inquest, and that issue for me, is still outstanding, until the coroner releases the findings of the investigation she ordered into that matter, which was publicly known after MSM published it.
For me, it didn't make sense that this seemingly intelligent couple would run the risk of obliterating their entire family at the side of the highway (not sure if it was a ramp or just the regular highway), in darkness, to pull over, presumably take the kids out of the vehicle, remove their pants, put on their pullups (even though – they were 3.25 and 4.5 yrs old - it wasn't like they were now going to drift off to sleep for an 8 hour drive or something). They had JUST visited inside a McDonalds with perfectly good bathroom facilities - surely they could have lasted another couple of hours before another bathroom break?
They picked up the kids from daycare at around 4pm-ish.. the kids were immediately put into the vehicle to start their 4-4.5(?) hour journey... three hours later (est), the fosters are expecting the kids to go to sleep? I could see them going to sleep if they'd commenced their journey at 7pm or 8pm or 9pm, but at 4ish, and being reportedly excited to be going on a trip and to visit with their FGM, and after having been confined in a vehicle already for 2-3 hours - would they be ready for sleep? And this pull-over on the roadway in the dark was so important, why? Leather seats (I’m presuming their Land Rover Discovery had leather) can clean up well, imo.
Is it possible it was prearranged to meet another party at the side of that roadside in the dark, where there were presumably no cameras, to ‘move him on’ to someone? Nobody knew what these people looked like, nor what vehicle they drove (in fact not until the inquest some 4 years later), nor did the public know where they stopped along the way exactly, so very unlikely that someone would report such a potential sighting so far away from FGM's house, imo. This, to me, is one example of how the secrecy surrounding the fosters has greatly hindered this case.