You have said this multiple times on this thread now, but in addition to how the OSI getting to unilaterally define the technical definition of "open source" being controversial even within the software engineering community, you really need to be looking at the definition of words "descriptively" and most people seem to put even "shared source" (look but don't touch) models as subsets of the class "open source".
Regardless: Copilot doesn't only pick up "open source" code... it picks up any code that has been published under any reason including the large amounts of code that is on GitHub without any license at all or which was literally stolen and leaked onto GitHub.
Meanwhile, even open source licenses have restrictions, whether they be "you can't use my work without agreeing to contribute back your work to the collective", various forms of automatic patent grants and associated retaliation clauses, or merely "you have to credit me", a simple limitation almost all open source software comes with which Copilot launders away.