Per another thread, this may not be the case for ferries? At least not for ones that don't turn around. (Note that many "people ferry" boats are able to turn around. Larger car ferries are fully symmetric and have no fixed bow/stern.

Edit: I found more discussion on this by searching for "double ended" boats. Port/starboard do indeed change depending on the direction of travel from all results I've found.

Hmm interesting. Wonder if they have some non-symmetrical parts, like the location of the engine maybe?

Sure. If nothing else, they've got labels on 'end 1' and 'end 2', and the rest of the boat is labeled into quadrants that don't change (A-D). If there's a galley, that's on one end or the other; the passenger deck is assymmetric.

The car decks and the sundeck appear to be mostly symmetric other than labelling, and maybe elevator placement? The machinery under the car decks is likely somewhat assymetric too, but I've never gotten to go down below.

Not the ones I ride. They have engines on each end.

To be fair, they may not be 100% symmetrical. I am not measuring. They are close enough that I can't imagine it would be a good use of the terms. (That is, when the VAST majority of the time the bow is the front of the boat, having a few bigger boats where I have to inspect it to know which is bow and stern would be a bad idea.)