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Answer
The NFC track does not need to be routed with a controlled differential impedance. The NFC antenna is different from the BLE antenna as it's differential and not 50 Ohm (each track is 50 Ohm single ended). Also, the frequency is very low, so the exact impedance doesn't matter as much. The inductance in the antenna is what matters for the NFC antenna. Since the antenna is differential, it's better to use a two-pin connection instead of U.FL which is a single ended connection.
The inductance of the antenna together with the NFC antenna tuning capacitors forms a resonant circuit that is tuned to the NFC frequency, 13.56 MHz. Any change in the connection wires to the antenna can be compensated with the tuning caps.