'Of course Moriori were pre-Maori'
I think I began my comments on this thread by urging you to find out about what Moriori themselves say, and about what scholars say, and by observing that Moriori do not and have never claimed to be pre-Maori inhabitants of NZ. The Moriori position is very clear: they are the tchakat henu (tangata whenua) of Rekohu (the Chathams), who arrived from tropical Eastern Polynesia, developed their unique culture in isolation on the Chathams, and only visited mainland NZ briefly to trade and intermarry with Maori.
Apparently you know something that they don't know, and that scholars would deny.
The idea that Moriori and Tuhoe were Melanesians who lived on NZ before Maori hasn't been held by scholars since the 1920s. I picked out HD Skinner's classic refutation of that theory recently when I made a list of NZ's best works of non-fiction:
Reading the Maps: Great non-fiction: another spinoff