The receptivity of high-speed compressible boundary layers to kinetic fluctuations (KF) is considered within the framework of fluctuating hydrodynamics. The formulation is based on the idea that KF-induced dissipative fluxes may lead to the generation of unstable modes in the boundary layer. Fedorov and Tumin1 (AIAA J., 2017) solved the receptivity problem using an asymptotic matching approach which utilized a resonant inner solution in the vicinity of the neutral point of the second Mack mode. Here we adopt a slightly more general inhomogeneous multiple scales (IMS) approach, based on a WKB ansatz, which requires fewer assumptions about the locus of primary excitation. The approach is modeled after the one taken by Luchini2 (AIAA J., 2017) to study low speed incompressible boundary layers over a swept wing. The new framework is used to study examples of high-speed, high-enthalpy, flat plate boundary layers (see Edwards and Tumin3) whose spectra exhibit nuanced behavior near the generation point, such as first Mack mode instabilities and near-neutral evolution over moderate length scales.