Highresolution Xray diffractometry is used to probe the nature of a diffractionpeak broadening previously noticed in quantum dots QDs systems with freestanding InAs islands on top of GaAs 001 substrates Freitas et al., Phys. Status Solidi A 204, 2548 2007. The procedure is hence extended to further investigate the capping process of InAsGaAs QDs. A direct correlation is established between QDs growth rates and misorientation of latticeplanes at the samples surfaces. This effect provides an alternative tool for studying average strain fields on QDs systems in standard triple axis diffractometers running on Xray tube sources, which are much more common than synchrotron facilities.