I know there's previously been lengthy discussion about whether or not a swashbuckler should or should not get an extra 1/2 APR for specialising in a weapon. There are views on both sides of that debate, but the following is definitely a bug:-
Observed behaviour: the level-up screen specifically tells us that the second proficiency point in a weapon yields an extra 1/2 APR, but that's an outright lie unless you're a Warrior class.
Expected behaviour: the in-game description and the game mechanic should match. EITHER the swashbuckler should get the extra 1/2 APR promised by the description in the level-up screen OR the description should be modified to say that this bonus only applies to Warrior classes.
Whichever side of the debate about the principle you're on, it's a definite bug if the in-game description promises a specific result and the game mechanics deliver a different result.
Personally I lean towards the view that Weapon Specialisation ought to mean what it (currently) says it means, not class-dependent (i.e. the 1/2 APR is part of the definition of Specialisation, so if a Swashbuckler can Specialise then he should get the 1/2 APR for it like anyone else). However, I can live with it being decided the other way (i.e. Specialisation means different things to different classes) PROVIDED THAT the game tells you correctly what you're going to get (or not get) for your particular class. The game lying to the player has got to be wrong!