I’m not too educated on the Maori Haka, so here’s a comment by a YouTuber from this video:
The way I was told, the haka was designed to psych out the raiding war party. It was done to AVOID bloodshed, which is something that’s gone unnoticed by a lot of history writers. The haka was also very practical in that it amped up the defending warriors so that IF the other tribe didn’t back down and run the other way, at least the warriors were all ready to defend their turf. Very practical people the old time Maori.
[EDIT: Image resizing issue fixed.]