What I find amazing, and a bit amusing, is that this Shi fellow possibly did not know, or understand, that all his actions on the corporate net are monitored and stored. Now, maybe he knew, did not care, and figured he would be long gone by the time Apple found out. Who knows? However, I would almost think that in the future, whenever an employee gives notice to leave, Apple will immediately review all of their keyboard activity. A bit surprised they don't do that already.
As for OPPO's response, that is the lawyer speaking. Now that the cat is out of the bag, I expect OPPO will distance itself from Shi, possibly end his employment, and throw him to the wolves. OPPO could quietly approach Apple, issue a mea culpa, terminate Shi, and license the technology. No harm, no foul. Mostly.
If OPPO brings to market any tech that vaguely looks 'Apple', Apple will be on them in a heartbeat.