@mszll It might be a small gradient difference and a factor related to the number of turns, the latter route has quite a lot (in their representation).
But in general yes their bike routes are not very good nowadays... in Sydney you sometimes get routed down Broadway because in Google's map it's a 'bike friendly road' - I think because bikes are allowed to ride in bus lanes.
I'm trying to switch to something OSM based but habits are hard to break.
@jroper yes most likely that plus the few m of smoothed cobblestone ("unpaved"). If so, it shows how bad street-logic based algorithms work for "weird" routes like bike paths that are decoupled from streets.