Whoops! I can answer my own question. :) I just called the toll-free number on the back of my Nutri-berries bag and spoke to Megan in customer service at Lafeber's. She said it's fine to give El Paso and the other varieties that are currently labeled as "parrot" to a parakeet. She said the nutrition and composition is the same, it's just the size of pieces that make up the Nutri-berry that differs. For instance, if they have peanuts in them, she said, it might be a peanut chip in small bird sizes and up to a whole peanut in macaw size.
I bought a bag of "El Paso for parrot" and "Tropical Fruit for Parakeet/Cockatiel/Lovebird/Conure." When I compare a Nutri-berry from each bag, I can see a teeny difference in particle size. It's not a huge difference, so don't be afraid your parakeet will have to deal with overly-large chunks. According to Megan, if the parakeet can handle the size #and it should be able to#, it's fine to give your Keet any Nutri-berries in the "parrot" size. My avian vet also recommended crushing the Nutri-berries with the bottom of a mug -put the berries in a sandwich bag first!- to break down the size for small birds just learning to eat them and I think that'd work if you found yourself with overly large pieces, too.
Megan from Lafeber's did say however, that Classic Nutri-berries and pellets are made of a different formula developed for the bird on the label. I didn't get more info on that, so if you're considering mixing recommended species' Lefeber's pellets or Classic Nutri-berries, you may want to check back with them. I don't think they allow me to give toll-free numbers here on a review so I apologize but the company can be looked up easily on the internet.