TBKMrt
Since this is the middle one, I will only write in this one (there is no use in keeping the talk going in three notes).

I would still say it's an OSRM problem. I have tested this in the local area where I live and it seems that OSRM does try to avoid motorways (or motorways above a certain speed). It will also choose a longer way around a certain area when it does not have to choose the motorway.
Even when you try to 'force' the line onto the motorway it reacts with some crazy loop ways.
Maybe we can get some help over at http://project-osrm.org/