This is one thing that bothered me. Sure, the tags are what they are, but a player is not worth more based on what position he is listed as playing.
One example a few years ago was Jimmy Graham. He wanted the Saints to pay him on the wide receiver tag instead of tight end tag. He argued he was split out wide more than half the time, so he should be paid as a wide receiver. I don't remember what happened. He might have signed before this was resolved.
But, he was exactly right. Back in the early days, the line was one center, two guards, two tackles and two ends. Then, they started splitting out one of the ends, so they became a split ends and tight ends. Later they lumped split ends in with the flankers and slot receivers (who are really backs) and called them wide receivers. By that definition, if Graham played over half the time as a split end, that's a wide receiver.