package_arcore was added to allow Chrome to selectively ship ARCore support to dev and canary while binary size issues were worked out. The solution for this is the AR DFM (862707).
According to tiborg, package_arcore really means package ARCore into the Monochrome APK and bundle builds always package ARCore support. (ARCore is not supported on older APK types.)
Thus, once the bundles and the AR DFM are enabled for all Chrome channels, we no longer need to worry about including ARCore support in the Monochrome APK and can remove package_arcore.
Comment 1 by bugdroid1@chromium.org
, Jan 18 (4 days ago)