The "completely deniable" part is not necessary for steganography.
Otherwise, you dismiss just about any examples of steganography prior to steganography on computers.
Which is fine, but as far as i know, not the commonly accepted definition.
Re:PNG and Hidden Pixels
by chrisseaton on Tuesday September 01, 2020 @10:04AM
(#24341800)
The question was
> so why bother
The answer is - because it's more deniable. You bother because more deniable is better.
Because these extra chunk are super-obvious? As soon as someone looks in your file they're going to wonder what you've added these for.
They will likely also not survive re-encoding.
The point of modern stenography is that you can't tell it's there, and it's just a part of the core image data, and that it's completely deniable.
How do you deny your nonstandard chunks?