Framer yes and I have posted the legal proof of that - the un named person should be listed by local airport rules or company procedures manuals and may well be the PIC.
But for this reason it is not possible for me to say who has authority or I would.
Now the regs cut and pated say a point in time that the PIC has authority, you simply need to know who that it is prior to that time.
Some company's may state it is the base manager or another title, and I very much doubt they will not give support for an emergency evac that you carried out without asking them.
But back more to the point of the offload and other normal routine things that pop up prior to pushback I.A.W the regulator the PIC may not be responsible or have authority.
It is up to the pilot to know who is the responsible person during this time not determined by the regulator.
Simply mate just produce the document as proof the PIC is in authority, it should not be that hard.
P.S Common sense, seniority and ability (the basis of your argument) are not regulations, rules or laws.