I lived in this area for nearly 4 years, so I'm reasonably familiar with this intersection too. Personally, I've never considered this to be a roundabout (hamburger or otherwise). I suspect however that the argument over whether or not this is technically a roundabout will never be completely resolved
Maybe a better question is 'Should this be mapped as a roundabout?'
My main focus when 'fixing' junctions to date has been to ensure Waze provides 'useful' TTS directions - not just correct routing. I have noticed that there are many junctions where it seems a lack of care has been taken over the geometry resulting in confusing spoken directions (an observation not a criticism btw )
With this in mind, the main issue becomes whether or not it makes sense to provide 'take nth exit' style instructions. Whilst there are junction layout signs that could be construed as roundabout signs on a couple of the side roads, it is not easy to identify the number of 'exits' from these - and when you reach the junction in moderate traffic, it is not easy to count the exits as you pass them. Especially considering
AndyPot2 wrote:2. It is possible (in fact you are directed) to turn right from the roundabout into the centre (ie onto the meat of the hamburger), I don't think we can map a hamburger roundabout to work like that!
Traffic flow is primarily lane based. If approaching from any of the other directions, there is no indication you are entering a roundabout (as Andy points out). In fact, many of the more 'local routes' virtually bypass the central round section altogether. As an example, A408(S) to Shepiston Ln is signposted (with matching road markings) as a left turn.
From this perspective, I would posit that mapping as a roundabout does not provide the best TTS directions - although I appreciate that fixing this is not a trivial task.
Observation regarding road naming
I would suggest (based on road signage and OS maps) the the A408(S) FW segment, should be labelled as the M4. Currently, directions for a route between Shepiston Ln & the M4 roundabout tell you to turn left on A408(S) - which contradicts road markings and signage. This would also apply to the A408(N) FW segment (even though in this instance it could provide less clear directions )
Note: This intersection now has 3 URs associated with it