According to a moderator of the IPP community, this is a bug. Unfortunately we have no way of tracking it.
"QBWG-18389 - DST is not showing correctly in TimeCreated & TimeModified Fields ... We do not have a way to track these externally."
Incorrect TimeModified Offset - Intuit Partner Platform Community (Edit: Aaaaand it's gone. This is now a dead link, perhaps the issue can be tracked down?)