Most internet information companies provide data and information based on formulas (logarithms) that name neighborhoods based on general areas. Because Piper Glen and because Piper Glen is larger than Pullengreen, it is used for the area name. Pullengreen is just across I-485 and only a few hundred feet separate Pullengreen...
Are you looking for certain homes in Pullengreen or Piper Glen? The reason they're showing as Piper Glen is because Trulia doesn't actually show the subdivision of the home, they just list the nieghborhood as the general area - that being, Pullengreen is in the "Piper Glen area" of Charlotte.
Pleaes contact me directly with questions about the area/market or if you would like a password protected access to run your own searches with more in depth information.