^^I have no idea, i know the official reason they exist was because of the success of the Daleks in the TV show, so they went big screen, got a big cast(Cushing), and filmed it in colour, which was the first time the Daleks were seen in colour, with the same the following year, then it would be 6 more years before they were seen again in colour with Pertwee's Day of the Daleks.
Its just a pity they did not make the third movie in the trilogy.....and as for fitting them into the Who universe, i personally simply look as Cushing playing a version of Hartnell's Dr.