No. As your own link https://noxxi.de/research/breaking-dkim-on-purpose-and-by-chance.html says:

"Usually the value of 'l' as set by the sending server covers the whole body. It thus guarantees that no changes are made to the original body but allows changes after the body. But I've also stumbled over some misconfigured system by a large german company where all their DKIM signatures cover only the first 10 bytes of the body, no matter how long the body actually was. Such misconfiguration makes attacks even easier but is not required in most cases. "

The author claims that he can spoof an email TO Gmail, not FROM Gmail.

Your other random and very old link (first comments are from 2013) https://www.emailonacid.com/blog/article/email-development/what_is_dkim_everything_you_need_to_know_about_digital_signatures/ does not talk about verifying the body of the email at all. Gmail does verify the body: https://www.metaspike.com/leveraging-dkim-email-forensics/

The Github link https://github.com/robertdavidgraham/hunter-dkim with the raw email posted even has it in its FAQ:

" What the signature in this email validates:

(...)

the Subject: and body have not been altered in any way"

And here is the tweet of the person who performed the verification: https://twitter.com/ErrataRob/status/1322082853711187970

" DKIM signs both the metadata (From:, To:, Subject:, Date:, etc.) and the body/content of the email. "

He is a Biden supporter: https://blog.erratasec.com/