As an attempt to clarify what was the reasoning behind this
decision we reached out to the project’s mailing list. Klaus Espenlaub, one of the VirtualBox developers, claimed that in 4.0.4 a field
was renamed for the sake of clarity and in 3.0.2 there were “more
intrusive” changes but that the removed methods were “not really
useful” and because this functionality had been made available for
a 10-day period (between version 3.0.0 and 3.0.2) they found “the
probability of breaking existing third party code was negligible” and
thus “decided it was worth it”.