I definitely believe that for the first N years of gcc the policy was absolutely necessary to drag vendors into actually contributing back.

Whether that's still true in terms of the trade-offs being worth it to maintain the policy in the current day, and if it's no longer true what value of N accurately describes when that changed, is something that I think people can reasonably disagree about.

(my extremely boring take being "there's so many counterfactuals here I'm really not sure")