You're both a bit wrong. It can use either QTWebKit or QTWebEngine at runtime. The latter is the default and is essentially the engine of chromium extracted from chromium without any google services or binary blobs (uses system libraries)... this is quite far from a chromium skin, it's not a fork of chromium, and it lacks more than the front end, it completely removes all of the privacy invasive features that has been troubling everyone recently.
This info on QTWebEngine is among the top comments on the page if you care to look.