I think its actually the anti-Tivoization stuff that they take issue with
"Early drafts of version 3 of the GNU General Public License (GPLv3) contained several patent retaliation clauses that varied in scope, some of which were later removed due to concerns about their efficacy. The final published version of GPLv3 contains a patent retaliation clause similar to those in the Apache License and Mozilla Public License, which terminates rights granted by the license in response to litigation alleging patent infringement in the software."
https://en.wikipedia.org/wiki/Software_patents_and_free_soft...
That would be a significant factor in avoiding GPLv3.