Mostly it’s just CYA for google since cycling is more dangerous than driving (due to the people driving), so there’s more surface area for them to get sued.
But yeah
turns and crossings that look safe on a map don’t have very much data on whether they’re actually safe, because google has a thousand times as much information about drivers than cyclists.
google sometimes suggests routes that can’t be traversed, legally or at all, by a bike. Same reason.
sometimes google suggests avoiding something a bike doesn’t actually have to worry about. This is actually the category of error I see the most: google sends you around something when you could simply walk your bike through it, or ride through it, because you’re not a car.