See https://reviews.freebsd.org/D22210 for details.
The patch attempts to silence spurious warnings about needing USES=xorg in certain conditions. Patch for exp-run is in the review.
A commit references this bug:
Date: Wed Nov 6 19:02:43 UTC 2019
New revision: 516921
Mk/Uses: Add USES+=xorg when including xorg.mk
Add USES+=xorg to the places where MK/Uses/xorg.mk is included from other
files in the Uses infrastructure. This is done to silence an erroneous
warning about USES=xorg not being set when using USES=gl, motif or xorg-cat,
even when it's included from the framework.
This is a different proposal than what was originally suggested in pr 241627
and https://reviews.freebsd.org/D22210 .
PR: 238988, 241627
Discussed with: mat
Differential Revision: https://reviews.freebsd.org/D22210
Closing this, since a different solution has been committed.