You are right of course. I was just adding another admittedly "remote" possibility.And when faced with 100% guaranteed loss of money implied in such upgrade, they have chosen to cheapen out and bought the most basic of Z490 motherboards there is out there. The guys who do such upgrades are enthusiasts and one can bet that they did their research properly.
Not only they will have Z490 that supports RKL, but most likely that mb will also properly support PCIE4 (again result of their research ) and have awesome power delivery components that were already required by 10th gen.
Just finished reading the Anandtech 11700K review.
Now I have to digest this...