This paper is aimed at exploring the implications of velocity-dispersion scalings on high-mass star formation in molecular clouds, including the scalings of Larson's linewidth-size ({sigma}-R) and ratio-mass surface density (L-{Sigma}; here L={sigma}/R0.5). We have systematically analyzed the {sigma} parameter of well-selected 221 massive clumps, complemented with published samples of other hierarchical density structures of molecular clouds over spatial scales of 0.01-10pc. Those massive clumps are classified into four phases: quiescent, protostellar, HII region, and PDR clumps in an evolutionary sequence. The velocity dispersion of clumps increases overall with the evolutionary sequence, reflecting enhanced stellar feedback in more evolved phases. The relations of {sigma}-R and L-{Sigma} are weak with the clump sample alone, but become evident when combined with others spanning a much wider spatial scales. For {sigma}-R, its tight relation indicates a kinematic connection between hierarchical density structures, supporting theoretical models of multiscale high-mass star formation. From the L-{Sigma} relation, cloud structures can be found to transition from overvirial state ({alpha}vir>2) to subvirial state ({alpha}vir<2) as they become smaller and denser, indicating a possible shift in the governing force from turbulence to gravity. This implies that the multiscale physical process of high-mass star formation hinges on the self-gravity of subvirial molecular clouds. However, the influence of turbulence may not be dismissed until large-scale clouds attain a subvirial state. This is pending confirmation from future multiscale kinematic observations of molecular clouds with uniform observing settings.