If you look at the circuit Johnw posted in https://www.diynot.com/diy/threads/manrose-timer-fan-circuit-diagram.652293/
for the Manrose timer fan (others are likely very similar) the switched live goes into a timer circuit with the permanent live straight to the fan.
The timer circuit actually controls the Neutral to the fan.
I suspect that this is a common circuit for most timer fans.
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