No the light in the F/TF are not CANBUS.
That is no the issue.
The interior bulbs dim gradually when turned off. This is done with electronics in the control unit.
However they were designed with normal filament bulbs in mind, and expect to see the low resistance of a bulb. An LED has a much higher resistance, and consumes much less power.
The control unit isn't switched (otherwise the bulbs would go out as soon as you took the keys out the ignition) and relies on electronic components to gradually reduce the power to the bulb to nothing. Unfortunately these are not perfect devices, and leak a small current (milliamps) when OFF. A normal bulb this would not be enough to illuminate the bulb, but because LED uses much less current (milliamps) it is enough to just get it to glow.
However CANBUS LED bulbs have a resistor built into them, to make the LED consume the same power as an ordinary bulb. (This is to fool the control unit on a CANBUS system to think there is a normal bulb there). However this resistor will also "drain" the leakage from the control unit to ground, so the LED will nit illuminate.
This is why CANBUS LED are often recommended when replacing these bulbs.
Unfortunatly CANBUS bulbs are larger than normal ones, and often struggle to replace these tiny bulbs.