Not that it really matters to me (because the site works how I want it to for the most part), but I'm confused 
by the "8 points per segment" explanation.
When I load the track I previously filtered down to 500 on bikehike.. it seems to be a single segment. Without splitting it before route creation:
If I leave in car mode it creates 75 via points (and leaves Rennes on the N12)
If I change to walk it creates 215 via points (and leaves Rennes on the D125
Yep, there is still only one segment. The reason it's generating more points is not because there are more segments.
When you use walking mode as opposed to car mode, the set of points that it's asking google for a route through is exactly the same set of 8 points. The difference is that in walking mode, google
needs to send back more route points to specify the route correctly, than it does in car mode.
Don't forget I'm not sending google the whole track - I'm only sending it the track reduced to 8 points. This is because it has a limit of 8 via points for a route request.
What it's doing there is saying "give me the route from Rennes back to Rennes, via these 8 points in between - in a car." In other words, if you were driving the audax and the controls were the 8 points that the track reduces to, then that's the way you'd go.
But by splitting it, what you're doing is saying "give me the route from Rennes to Montfort-sur-meu via these 8 points that are
between Rennes and Montfort-sur-meu (rather than spread out between Rennes and Rennes)
and then, do the same from Montfort-sur-meu and ... (the next place you split it).
If you split it into 5 segments, it's making google do 5 times more work than it is if you leave it as 1.
Why walking gives more points:
To give an analogy: if I drew a track from nottinghamshire to penzance (that just happens to, for the sake of argument, reduce to newark, leicester, coventry, birmingham, gloucester, bristol, exeter) then if you asked me to describe the shortest route there via those 8 places I would say, right - A46, M69, M6, M42, M5, A30. There you go - only 6 route points. But if you asked me to describe the way
walking via those *same* 8 places, then it would contain a lot more than those 6 points as you wouldn't go on motorways but would take a much more laney route.
Now, if instead you first asked me to route to leicester, via 8 little villages between here and leicester, then even in car mode it wouldn't just go straight down the A46 because it would have to go through all the little villages.
That is how I intended the create route function to work. And I am hoping users get into the habit of keeping tracks logically grouped into segments as they make sense for other purposes (rerouting, elevation, etc) as well.
However, it's often unclear that (especially with tracks created elsewhere) the splitting process is necessary for the route to be vaguely accurate to the track - so I will look to making it more automatic; it's only a first stab so I can certainly adapt it to make it easier for users.
Using walking mode is sort of "cheating" - it's the wrong way of achieving the end of getting it to generate the increased amount of points that you want. The only reason it's bad is that it could route you down a footpath that is uncycleable (albeit legal in france iirc.) But it's understandable, it's not your fault - I should make it less cumbersome to do it using car mode (which imho it should be), as it is it's a bit of a burden on the user to have to split it down into separate segments in order to get the route to be accurate.
What I will probably do is instead of simply using 8 via points per each segment, use 8 via points per 50km or so - no matter how many segments there are. I suppose it would be good for me to keep my eye on the fact that while the user may want to split tracks into segments, they shouldn't
have to understand segments in order to use it.
