Apparently not enough protection given that the judge has given an order for the source to be revealed.
https://www.courtlistener.com/recap/gov.uscourts.nysd.525673...
Apparently the standard here for piercing reporter's privilege is pretty simple:
“The qualified [reporter’s] privilege can be overcome only upon a clear and specific showing by the party seeking disclosure that the information is: (1) highly material and relevant to its action; (2) necessary or critical to the claim; and (3) not obtainable from other sources.”
My takeaway from this is that if you think it's likely that a statement you are making to a reporter will be the central subject of a legal action (e.g. if you want to slander someone to a reporter), it is not a safe move.
Of course, this doesn't mean that the investor will prevail overall. But it does seem like the confidential source will have to defend the truthfulness of the material they provided in court. IMO, this is not an entirely unreasonable outcome.