Who has something to gain by duping Bloomberg
Skeptical of the short theory - the SEC can track that too easily since Supermicro is the only target you could reasonably short. Who else could be duping Bloomberg, and why? They said they talked to the FBI, and I'm sure they'd connect to their sources through the FBI main number at least once to verify they really worked for the FBI.
Given the divide between the Trump administration and the FBI, I suppose its possible if the administration had a few people within the FBI make these claims, supply contacts with "Apple" and "Amazon" that weren't, to fool Bloomberg into posting this story. It is quite timely given Trump's battles with China - maybe the idea was to get the public behind his trade war even things don't turn out as rosy as Trump naively believes.
For Trump's admin it is no lose - if they get away with it they get the public on their side even if the China trade war gets messy and long lasting, If they get caught they blame the FBI and say see "this is proof they are incompetent and the top people should be fired" so they can sabotage Mueller's investigation.