I tested my 2021 with the FOB in the front passenger seat and back seat and it disappointingly starts just fine. This car has at least two interior antennas to detect the FOB and typically for a car this size there would be at least three. The scenario it should be trying to avoid, not unlike the OP's situation, is doing a curbside drop-off of somebody at work or the train station, and THAT person has the key in their pocket.
I double checked my Flex and it gives a "no key detected" message. And as mentioned, the ID.4 seemed to not drive any further, despite being in D, when I stopped and set the key out the window. I'll have to test that one more, because that also doesn't seem ideal (ex. FOB battery dies).
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