This is just blatantly false. The gerrymandering in Wisconsin was what was taken to the Supreme Court in the political gerrymandering case, precisely because it heavily favored Republicans.

The Supreme Court ruled against the plaintiffs (not surprisingly, 5-4 I might add), but in the grounds that the federal courts didn't have the power to intervene in cases of political gerrymandering, but no one really debated that the Wisconsin maps heavily favored Republicans over what a more normal, compact map would produce.