No, wrong answer. They're not usable as blocks, but they do carry meaning, in the long form input dialog, where they label the input types.
Oh now that I can run the program I see the point of the question. Yes, they're without purpose as blocks.
I am running Monterey (12.4) on Intel. I downloaded Super-Snap!.app from your Google Files pointer, unzipped it, and it wouldn't run at all until I changed the permissions of the actual executable inside it. Then it crashed. Did I download the wrong thing?
Oh, I see it. The app is unauthorized for every Intel Mac! 
I have a secure copy of Super-Snap! in my desktop.
I'm uploading the copy to my principal account instead.
? Link? Tnx.
Now the file is a .zip one and is now updated to the actual GitHub version of Super-Snap!
No more "Scratch Cat" and no more "Gobo".
Alonzo, Sparrow and the Streak costumes are the only costumes who are free to use.
Yay! I can run it now.
How do I access those costumes? (Also, you need help screens, or at least help texts, for many new blocks that I can't figure out, such as that C/P one.)
The costumes of Super-Snap! are inside of the app.
See: Super-Snap!\Super-Snap!.app\Contents\Resources\app.nw\src\default-costumes\
The help screens are not present, because I'm editing them...
but that's so long to produce them manually in good SVG quality. 
Remember that:
In the folder of Super-Snap! you can open the Examples folder, focus on the Projects and you
can get the Super-Snap! example projects; some of them are good old BYOB recreations.
I saw that, but how do I actually get one into Snap!? Open the folder in Finder and drag one in? I was expecting a Costumes menu item.
NOOOO!! why did you do this to them? :(
Oh, probably for legal reasons, I assume, but still NOOO 
Scratch Cat and Gobo are Scratch Trademarks, and cannot be used without explicit permission from the Scratch Team:
According to Scratch FAQ:
There are a few exceptions: the Scratch Logo, Scratch Cat, Gobo, Pico, Nano, Giga, and Tera are Scratch trademarks, and can not be used without explicit permission from the Scratch Team.
quoted from May I use / remix Scratch support materials, sprites, images, sounds or sample projects I’ve found on the website? question.
I know.
Also, I just now realized that their names:
all represent byte sizes.
To waste your time...
Picobyte = 1k nanobytes
Nanobyte = 1 billionth of a byte
Gigabyte = 1 billion bytes
Terabyte = 1k gigabytes
Nice detail.
If that's the definition of a nanobyte, then wouldn't a nanobyte be useless? (You can't have
(* ( / 1 8 ) (^ 10 9) ) bits.) I always thought they were named for sizes of units in the metric system.
Yes. You can drag the default-costumes folder to anyone of your preference.
That folder is not necessary for the Super-Snap! itself. 
Sadly, the Scratch Team has reason about deleting these costumes. 
Fortunately the rest of the costumes are not. Here is the descriptions of them:
Alonzo: The essential mascot of the entire Snap! software. He is so cute and friendly. 
Sparrow: This is a little furry mascot from Dango,
a deleted Scratch mod that includes lambda blocks. 
Streak: Is the mascot of the Scratch-1x mod from the same name.
This is the unique mascot that any pen can draw to take its appearance. 
I've never heard of Dango and Streak. Are there any download links / websites for them?
The only thing I have is the images in your source code:
- Streak
- Sparrow
For Streak is: https://web.archive.org/web/20160404082923/http://billy.scienceontheweb.net/Streak/
And for Sparrow... (Dango), the link is dead:
The only resources remained of Dango are the costumes, so these are saved from being deleted. 
Why didn't you include all the costumes? We have gazillions of them, mostly taken (legally!) from Scratch. And then there's Jahrd, Derec, Jamet, Sarron, Aleassa, and Tad (and soon Lirin, when I get around to installing them), which aren't from Scratch, but licensed to Snap! by the artist, Meghan Taylor. (If you use those, keep the paragraph about them from About>Credits.)
Why this Scratch mod deleted? 
very cute... :3
very cute indeed!
They should've added the source code to GitHub so it would never die.
Guess I have to remove the link to my Scratch profile from my website. It uses the little S version of the logo as the link text.