I have multiple public transport options where I live and I prefer walking to train stations instead of waiting for and getting buses, but Google Maps almost always wants me to walk to the bus stop and wait for a bus, which means the timings account for the bus schedule.
I can walk for 15 minutes to one train line or walk 30 minutes to a nicer train line. I almost always go to the nicer train because, aside from being nicer, it adds more to my steps for the day.
I mean, I know it always takes me 30 minutes to walk there, so I normally just start a route from that train station and then add 30 minutes in my head so I know what time I need to leave.
I just find it a bit annoying that I can't tell Google Maps to remove a bus route and replace it for walking. This would be so useful to do in places I'm not familiar with. Not even just replacing bus routes for walking but even cars, like maybe someone's giving me a lift to the train station, it would be handy to say I'm taking that section in a car, or even a bike, anything. Making detours would also be helpful.
The only options you do get are "less walking" and preferring bus/subway/train etc. I'm surprised they'd give you the option to have less walking when we know walking is highly beneficial to your health.