I believe they’re just using raw speed data from other cars, which ia why it appears yellow or red when you approach a light & there are no other cars around.
There are a couple of places near me tvat are always backed up, basically where two highways / interstates cross or merge; makes sense as all of the additional cars slow down until thwy can space themselves out again. Ive had Maps show that as as red with the crash symbol. Nope, not an accident, just normal traffic flow that backs up for .x miles. I’ll reroute around a crash but there is no need to f9r a normal merge delay.
Ive seen it do that to me, usually unnoticed. Why can’t ut be LOUD about ut that do do it automatically it i don’t notice the screen for the few seconds before you reroute me. I know i have 10, 20, 50 miles left on this road so i can just pay attention to driving…or at least I did until you did a stealth direction change. While we’re at it, when i put in my destination you gave me three options, I chose route B for whatever reason, don’t then tell me you found a faser route (A) as i already rejected that once.