ARCANIST env variable is not set for pre-commit hooks

After the ⚙ D20990 Collapse Arcanist toolsets from "wilds" into "master", as an overlay layer the env variable ARCANIST (⚙ D7281 Write ARCANIST into the environment while running arc) is not set and accessible during commands like arc land for use in pre-commit hooks.

Was this functionality removed intentionally? If yes, is there other approach how to distinguish arc usage in git hooks?

Reproduction Instructions
arc land in a repository with pre-commit hook, that expects ARCANIST env variable to be set.

Phabricator/Arcanist Version
arcanist 7af9846f994a8d0a1fc89af996e3ddd81f01765e (26 Mar 2021)