Under the statutory and regulatory notice requirements governing VA decisions since 1990, is the VA permitted to retroactively deem a claim "implicitly denied" when the agency never issued a notice explicitly setting forth the claim at issue or the reason for its denial?

Whether the Department of Veterans Affairs is permitted to retroactively deem a veterans' benefits claim 'implicitly denied' when the agency never issued a notice explicitly setting forth the claim at issue or the reason for its denial, in violation of statutory and regulatory notice requirements under 38 U.S.C. § 5104