There's an errata update for 6.2 - xpdf-0.91-1.6x 7.0 ships with xpdf-0.91-1 Because RPM considers the errata update to be of a lower version than the 7.0 release, the upgrade path in the installer winds up not upgrading the xpdf package with the 7.0 version, that contains FHS-compliant install loaction.
This problem is fixed in xpdf-0.91-2.