The recently derived Fourier-Matsubara expansion of imaginary-time correlation functions comprises an exact result of linear response theory for finite-temperature quantum many-body systems. In its density-density version, the expansion facilitates systematic comparisons between quasi-exact ab initio path integral Monte Carlo simulations and approximate dielectric formalism schemes at the level of the imaginary-time (density-density) correlation functions and the dynamic Matsubara local field corrections. On this theoretical basis, the dynamic properties of the quantum version of the Singwi-Tosi-Land-Sj & ouml;lander scheme are analyzed for the paramagnetic warm dense uniform electron gas. The marginal improvement compared to the semi-classical version of the Singwi-Tosi-Land-Sj & ouml;lander scheme is attributed to the weak Matsubara order dependence of the approximate dynamic Matsubara local field correction. The evaluation of the ideal density response function at the non-interacting occupation numbers is identified to constitute a general deficiency of the dielectric formalism, which calls for a reformulation in future works.