Lore

No. There's nothing that says Nemeton and Pincara are the same. Edit:Also forgot to mention, but there are times when TH talks about some things on the slate can't be read. So we're missing some parts.

And Cessair in the original lore only designs one person, the leader of the first settlers. Though I did read some things that describe them as the first settlers.

A better comparison would be that.

Ban Clan = The first settlers of Ireland

Pincara = Ireland, as the First Settlers were denied a spot on Noah's Arc to safety.

Except not even Ireland could protect Cessair from the flood. God being Neamhain, the flood being the curse.

Though that's just my crack comparing.

Also Crack Theory:

The Ban Clan call their banishment as their first punishment. But while they do name the other things that happened to them, they do not describe those as the second punishment. Why? Because their curse was caused by the curse on Iria. How do we enter to Nemeton? From Metus, in Iria. We only hear what happened to the elves and giants, except that's the whole point. The people had forgotten the Ban Clan and thus their involvement with whatever in the past is gone. Neamhain destroyed ancient relics during the curse, most likely belonging to the Ban Clan.