Good call! You're right that "continue straight" might not be the best wording, as they aren't aligned on the map. In real life, they're also not perfectly aligned, but the entrance area to the tunnel is much wider than appears on the map, meaning they can take a slight right to continue down the tunnel. My bet is I was thinking about roads in terms of Boston roads, where going straight is often more of an abstract concept than a true direction.
Here's a streetview with Bennett Alley on the right and the bus tunnel on the left if you want to get a feel for the turn:
The streets are not aligned, are they?