Syllabus of Errors of Parmenides

I've been troubled by Parmenides recently. I thought I understood him but now doubt that I do.

On a lark, I googled 'Parmenides' and found lecture notes which, after giving a reconstruction, conclude:

7. A summary of Parmenides’ errors:

a. He thought that what does not exist could not exist (possibly confusing this idea with the truism that, necessarily, if something does not exist then it does not exist).
b. He thought that denials of existence are impossible (i.e., they cannot be both meaningful and true)
c. He thought that all denials, all “is not”s, are denials of existence.

One might have thought, rather:

7. A summary of Parmenides' errors:
a. He thought that only one thing exists.
b. He denied change.
c. He denied imperfection.

(Frankly, I was a bit surprised to find philosophy lecture notes which simply say, outright, that controverted philosophical views are 'errors'. No, these notes are not from a class given by an emeritus writer of scholastic manuals.)