resolveToConfig indicates that the ad may be displayed in a FencedFrame. This only makes sense to be specified by whoever invokes runAdAuction, so top level, although component auctions can also specify it with no effect that I can tell.

URLs to be loaded in a FencedFrame require special headers and behavior (no access to top window for navigation etc). Therefore this signal is useful if not necessary for ad selection and even scoring in component auctions. Otherwise, an auction winner may ultimately be blocked from loading in the FencedFrame after having triggered all the win events so as to appear that it was a billable event.

One approach may be inheriting this flag from top level to expose it in browserSignals for both generateBid and scoreAd.
Another may involve the same type of filtering done for ad formats and requestedSize.