"A new type of shell" is a bit of marketing text to express the fact that this shell doesn't follow in the footsteps of most other shells (bash, zsh, fish, etc) in terms of treating things as blobs of text (which allows for a number of innovations). The fact that the author even states that it's partially inspired by Powershell demonstrates that he's aware of the similarities (and has in fact cribbed many ideas from it).
Calling his marketing line "disingenuous" comes across as very petty nitpicking that adds nothing of value to the discussion.
The part that bothered me was not that they described something that shared some concepts with PowerShell as "a new kind", but that I did not see any illustration of entirely novel features in the examples that followed. As a sibling comment remarked, they feel I'm quite mistaken, and there are very positive distinctions illustrated in the examples, but I took a look at them again, and it's still not clear to me what they mean.
I think I don't see why it's unreasonable for something which advertises cross-platform support to be compared to common shells on all those platforms, not just originally-*ix ones? That is, I think it's totally reasonable for you to think the tagline is justified solely by the differences in those shells, even if I disagree, but I don't see why you think it's unreasonable for me to hold this view?
FWIW, I don't think "it's marketing" is a valid excuse for them saying things that aren't true. It's not a "new kind of shell" because it's mimicking things that already exist. The author even knows about those things and cites them.
I do not accept the idea that it's okay to make false claims to create a narrative, marketing or otherwise.
My initial interpretation is that this is a level beyond typical nitpicking, but I'm not sure how that follows?