Since #1452, the command structure is now fully removed when an app is unloaded (and therefore regenerated on reload).

Therefore it should be possible to capture the host when creating it instead of querying it from the host map, because it won't change during the lifetime of the command.

This isn't the case right now because previously the command would be kept even between app reloads (due to Brigadier limitations), meaning we needed to query for a possibly different host on command execution.