The tap plates on a flamenco guitar are indeed to protect the soundboard from the guitarist's fingernails, but not just because the nails may hit the soundboard by accident. A standard part of flamenco guitar playing is to tap the soundboard with a right-hand fingernail to produce a percussive effect, emphasizing specific rhythmic stresses. This is called golpé, and the plastic plates are to protect the soundboard. They are called golpéador.

How to play golpé.

More, including an intro lesson.

Don Firth

P. S. "I generally crash and burn somewhere in Leyenda but it's not the guitar's fault." I know what you mean! I still can't get through it without starting to wheeze a bit. I did get Requerdos de la Alhambra down to where I could do a halfway decent job on it.