Let x be a normalised standard complex Gaussian vector, and project an Hermitian matrix A onto the hyperplane orthogonal to x. In a recent paper Faraut [Tunisian J. Math. 1 (2019), 585-606] has observed that the corresponding eigenvalue PDF has an almost identical structure to the eigenvalue PDF for the rank 1 perturbation A + bxx † , and asks for an explanation. We provide one by way of a common derivation involving the secular equations and associated Jacobians. This applies too in related setting, for example when x is a real Gaussian and A Hermitian, and also in a multiplicative setting AU BU † where A, B are fixed unitary matrices with B a multiplicative rank 1 deviation from unity, and U is a Haar distributed unitary matrix. Specifically, in each case there is a dual eigenvalue problem giving rise to a PDF of almost identical structure.