Nothing is straightforward with HNA. Some frames have been in that area for months. They may not have decided which airline will operate this frame. Airbus may just be waiting to see if HNA can pay and want the frame out of the way.
How can it be that this frame is in the delivery process without being fully painted? Has this happened before?
To answer your question: no, this hasn't happened before with A350s.
But we learned from 246, 251, 260, and 285 recently, none of them are going to the airlines fcs that they are wearing. They all been sold to lessor.
So if the lessor need to repaint these frames anyway, they may not care about whether they've been painted already before delivery. So I expect 270, 283, 299 and 308 could all been delivered unpainted.
Another guess is, for Airbus to agree on change of ownership at this late stage of production process, Airbus may have insisted that the lessor to follow existing delivery schedule, so to pay and take delivery regardless whether the lessor have found a new operator or not. If this is the case, it will explain why 246, 251, 260 and 285 are all sitting in TLS.