Sending custom file via Airdrop: using exported UTI or imported UTI?

Question

I have googled a lot about this. In my experiments I find either worked fine. I'm currently using exported UTI in my app. But then I found this Apple document, which suggested to use exported UTI. I wonder is it OK to just keep using imported UTI, or do I have to use exported UTI, or both? The file is only used for transferring data. It's not supposed to be saved as a file.

I also find this highly rated answer, but not very sure how to interpret it. I suspect my confusion might be caused by the fact that these things were introduced for sharing files not for transferring application specific data.