The work product doctrine involves many more varied and practical aspects than the attorney-client privilege. Among other things, heightened opinion work product protection can sometimes protect lawyers' selection of intrinsically unprotected documents, witnesses, etc. -- if the adversary has equal access to them, and if the selection would reveal the lawyers' litigation strategies. Many courts call this the Sporck doctrine. Sporck v. Peil, 759 F.2d 312, 315 (3d Cir. 1985).
In Boston Scientific Corp. v. Edwards Lifesciences Corp., Civ. A. No. 16-275-SLR-SRF, 2016 U.S. Dist. LEXIS 178515 (D. Del. Dec. 27, 2016), defendant proposed a protective order provision requiring the parties to identify any documents they planned to share with foreign lawyers. The court denied defendant's proposal, citing Sporck in concluding that "[t]he procedure described in [defendant's protective order provision] would reveal which documents are important to Plaintiffs, and therefore disclose information that is considered work product." Id. at *5-6.
Lawyers should be on the lookout for their adversaries' seemingly innocuous discovery of, or other references to, intrinsically unprotected documents, witnesses, etc. – if the discovery or other reference might reveal the lawyers' opinions or litigation strategies.