“The wood used for its construction was cut down in the years 913 and 914..”
“The tree was cut down in 980, during the reign of Duke Mieszko I, the first documented ruler of Poland.”
Unless bark is present, the radiocarbon date doesn’t and can’t show anything of the kind (apart from an unverifiable coincidence).
No one is talking about radiocarbon dating. We are talking about dating by treerings.
The 913 and 914 dates are for the wood used in the bridge.
The 980 date is for wood used in the shore fortification.
The author makes it clear the year is for the date the tree was cut down.
The artifact could have been made later.
Of course it is radiocarbon dating. Modern dendrochronology is reliant on radiocarbon dating.