We present asymptotic and numerical solutions for the axisymmetric diverging radial flow of a viscoplastic Bingham fluid in narrow gaps of varying thickness. The asymptotic solution by Muravleva (2017) is used, which is compared with the finite element analysis result. The result clarifies the recent confusion discussed by Zou et al. (2021) and the articles referred to therein. The viscosity regularization error is also discussed briefly. The flow kinematics is investigated by using the non-persistence-of-straining tensor developed by Thompson and Souza Mendes (2005). It is noted that the local kinematics of the diverging radial flow can be significantly affected by the variable gap thickness, especially in the pseudo-plug region.