There's a reference to PhutilHighIntensityIntervalDaemon in https://we.phorge.it/source/phorge/browse/master/src/infrastructure/daemon/PhutilDaemon.php$34
That class seems to have originated from libphutil and then never been merged into Phabricator or Arcanist when libphutil was scrapped. That reference should probably be deleted, unless the class exists somewhere else.
Discovered this while working on https://phabricator.wikimedia.org/T366377