Its value is determined by HAVE(AVSAMPLEBUFFERDISPLAYLAYER_COPYDISPLAYEDPIXELBUFFER), which is true since macOS 13.
rdar://117600011
Pull request: https://github.com/WebKit/WebKit/pull/19653
Committed 269970@main (cbabd1ef63fe): <https://commits.webkit.org/269970@main> Reviewed commits have been landed. Closing PR #19653 and removing active labels.