I finally got my two apps approved, they both required an initial fetch from Firebase Storage. I don't know if Apple has resolved the issue, or they actually tested on a cellular connection, as i requested they do, if they encountered any issue. I also referred to this thread in the reviewer notes.
nikolajt
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So I ended up finding a workaround dy first calling "Select", and then using the .select flag instead of .addressed.
iso15693Tag.select(requestFlags: [.highDataRate, .address]) { (error) in
if let error = error {
session.invalidate(errorMessage: "Failed to select")
return
}
iso15693Tag.customCommand(requestFlags: [.highDataRate, .select], customCommandCode: 0xA2, customRequestParameters: Data()) { (data, error) in
		...
}
}
Maybe there is a bug in the customCommand function when using addressed mode?
I also did a quick test on Android using the transceive() method, and had no problem sending custom commands in addressed mode.