I was dumping a bunch of money on the formulatron in Dalimond trying to get platemail armor formulas I am missing and I ended up with several extra shield formulas. I tried to sell the ones I couldn't use on the consigner and found that they are attuned.

Why are these attuned? But none of the other formulas from the formulatron are?

The ones I found are:
Beginner Heavy Round Shield
Beginner Round Cross Shield
Beginner Round Shield
Beginner Reinforced Round Shield