In my view, no. Yes, they maintain a certain distance when relating to strangers, a coolness that an outgoing American can find off putting. And yes, they are insistent on adhering to a set of formalized manners. And true, they have a concept of personal space that can make you feel uncomfortable if you are used to a world in which the 15 inches surrounding your body are inviolable.
But rude in the sense that they lack consideration for others? Not at all. On the other hand, it seems to me that maintaining a certain level of decorum in interpersonal relationships requires a pretty much constant stream of reminders about what's proper. This notice, with its tut tut tut instructions to treat the bus driver with respect, is part of a campaign to keep bus riders in line. Other notices in the series admonish riders not to ask the driver to stop between stops, to give up their seats to persons who are older or infirm, to fold up their strollers, and to keep their voices down. There's even a series of borderline ridiculous YouTube videos to reinforce the messages.
Has this campaign made any difference? As you might guess, I'm skeptical. But I don't mind the intent. And I'll try to model the proper behavior the next time I'm on the bus.