I wouldn't interpret what he said as a major face-lift. What was said is that there are changes with the cockpit and the internal structure. These changes aren't going to be observable from the outside.
The engineer is likely right, someone mentioned more composite structure, which is usually a weight saving measure, maybe changes to streamline the eventual manufacture, and possibly software, etc changes for FCS as they are just getting in up to their elbows on the J-20 flight test regime, likely high alpha and probably pushing top end as well, so plenty of tweaking goes on in this stage with all aircraft. The F-35 is just beginning her high alpha testing, so she may see changes as well and likely will. AFB