Shield Proficiency question

[Llyarden]

Does Shield Proficiency only work with one specific shield, chosen when you take it, or does it cover all shields?

Shield Proficiency wrote:

Benefit: When you use a shield (except a tower shield), the shield's armor check penalty only applies to Strength- and Dexterity-based skills.

The feat itself says nothing about selecting a shield, but then (emphasis mine):

Taldan Duelist wrote:

Prerequisites: Dex 13, Exotic Weapon Proficiency (falcata), Shield Proficiency (buckler), Weapon Focus (falcata).

Apparently this feat thinks differently. My instinctive response would be that Shield Proficiency covers all shields, and therefore would be considered to include Shield Proficiency (buckler), but is there actually anything to support that? I've fallen foul of some unexpected rulings before, so I'd prefer to check.

[Chess Pwn]

The feat is all shields except tower shields. But the swashbuckler has proficiency with the buckler and not other shields, so he meets the requirements.

[Nefreet]

With feats like Weapon Focus and Improved Critical (as examples), they call out that the feat only allows one choice.

With feats like Shield Proficiency and Simple Weapon Proficiency (as examples), you gain access to the entire category.

Those proficiencies are so basic that nobody would choose them as feats otherwise.

[Llyarden]

Ah, I forgot about characters being proficient with bucklers only. That would be why.