We cannot discuss why CoreNFC is not available from app extensions. It just isn't. We cannot discuss future plans either. If this is important for your use case, we always welcome feature requests via the Feedback Assistant There are no ticks, workaround, or entitlements to make CoreNFC work from an extension. Nor it is possible to launch the main app form an extension. Your option 3 of the main app performing the NFC functions and then sharing the data with the extension is about the only way this would seem to work for your use case if I understand it correctly.
Topic:
App & System Services
SubTopic:
Hardware
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