These are bluffs enough for the call to be at least neutral. You don't have to win it very often. Passive players bluff passively too and since the bet is designed to not look like a bluff it is effective for him. I call this all day as played.

If we're folding to this small bet on the river can the flop raise be right? If he is so tight and passive that this river bet means we're beat then what does his flop lead mean? Would he lead flop with a draw or a worse A here? If not then folding or calling on the flop are both better than raising I would think. The less likely we are to be ahead then the less value in protecting obv and finding out where we're at isn't a good reason to build the pot.

If he is that passive you could fold the flopbut that is probably too weak. I would prefer calling the flop and folding turn if he fires again, or bet turn if checked to. This line would get you away from his stronger hands cheaper and allow us win the pots when he is drawing or has a worse hand. Assuming he plays it straight forward.