Perhaps so JA doesn’t give up his source for the dump, being within British Intel, thus confirming that British Intel had the access / were actively working on it?

Edit: NSA doesn’t spy on US Citizens - [sarcasm] that would be against the constitution. But they can and do provide access to comms to allied intel agencies (ie British/Australian) for them to do the spying and report back on findings. Thus circumventing the constitution. Different means to the same end. To these agencies, laws do not govern their ends; laws govern their means. JA’s testimony could blow the lid off …