Does Shield Master make Two-Weapon Fighting obsolete?

Question

I need a clarification between these two answers: 1 2

• The first answer argues that Shield Master removes only the penalties from attack rolls made with a shield. So for example a character that has the Shield Master feat, has a Bonus Attack of +6/+1 and is armed with a longsword (primary) and a light shield (secondary), his full-round attack would look like this:

  +4longsword/+6lightshield/-1longsword

  or

  +2longsword/+6heavyshield/-3longsword

  with a heavy shield.

• The second answer, which is corroborated by an official FAQ answer, seems to argue instead that Shield Master removes all attack roll penalties made when attacking with a shield. So, again, a character that has the Shield Master feat, has a Bonus Attack of +6/+1 and is armed with a longsword (primary) and a light shield (secondary), his full-round attack would look like this:

  +6longsword/+6lightshield/+1longsword

  or

  +6longsword/+6heavyshield/+1longsword

  with a heavyshield.

  Which would effectively make the feat Two-Weapon Fighting (although essential to the acquisition of Shield Master) and light shields' powerplay (except for the fact that, unlike heavy shields, you can hold small objects with a hand equipped with a light shield) obsolete.

• A third answer (which I came up with, based on the fact that a lot of people think that corresponding primary and secondary attacks happen at the same time) may be that Shield Master removes all attack roll penalties, but only when attacking with a shield. So, same character with Shield Master, Bonus Attack of +6/+1, armed with a longsword (primary) and a light shield (secondary), his full-round attack would look like this (the first two attacks happen at the same time and a shield is involved so Shield Master is applied, the third one is believed to happen separately so it doesn't benefit from the feat):

  +6longsword/+6lightshield/-1longsword

  or

  +6longsword/+6heavyshield/-3longsword

  with a heavy shield.

Which one of these outcomes is the correct one?

Answer 1

You only remove the penalties on shield attacks

Your understanding of the FAQ on the second answer is wrong, it says it removes the penalties when attacking with a shield, not when attacking while wielding/wearing a shield. To clarify, let me quote it again:

Shield Master: When Shield Master says “You do not suffer any penalties on attack rolls made with a shield while you are wielding another weapon” it seems like in context it means you don’t take the penalty for Two-Weapon Fighting, but it just says “any penalties” so it isn’t clear. Which penalties does the feat let a character ignore?

Shield Master allows a character to ignore the Two-Weapon Fighting penalties on attack rolls with a shield while wielding another weapon, but not any other penalties.

When you are attacking with a longsword, you are not attacking with a shield. Those are separate weapons and separate attacks, so the Two-Weapon Fighting penalties apply normally to your longsword attacks, but not your shield attacks (thanks to Shield Master).

This was clarified by Jason Bulmahn (Lead Designer back then) before that FAQ and the feat errata, which said:

Does Shield Mastery remove the penalties for all attacks if you are using a non-shield weapon and a shield and two-weapon fighting? Or does it only remove the penalties for the shield attack?

Shield Mastery only removes the penalty for Two Weapon Fighting on the Shield Bash itself, it does not remove it for a non-Shield weapon in your other hand.

This is only quoted here and there, but the actual link to that was actually broken sometime when Paizo upgraded their website in the past decade, so there are no direct links to this quote, and it cannot be found when searching their website. So, I believe this was archived or deleted and can no longer be found.