I copied and pasted your text into my terminal - I couldn't see a difference and still can't but there must be one since I get a different error message:
"find: invalid mode '0600)'
That gets me the same error message with the forward slashes:
find ~ (-type f -not -perm /0600) -or (-type d -not -perm /0700) | wc -l
find: invalid mode ‘/0600)’
Deprecated... that is very interesting. Where did you look it up? My book is from 2019 so this must be recent.
cc
OK I believe I've figured out why Jeslin's command syntax works and mine does not. In Jeslin's post, he's separated every parenthesis and argument with a space.
So Jeslin's: "find ( type f...." works OK
And my "find (type f..." does not.