I'm missing something, perhaps is the understanding of demonstrative pronouns. In (from youtube)
That is Peter. or
Das ist Peter.
Das is being used as a demonstrative pronoun, right? But the case, is it neutral? Shouldn't it match with Peter? Then would be
Der ist Peter.
And (to confuse me a bit more) GERMAN DEMONSTRATIVE PRONOUNS “JENER” seems to translate
that also. Perhaps I should say
Jener ist Peter.