Unfortunately I must agree that adding the “s” is the predominant form these days, though it is superfluous and awkward. The contrary, alas,
Minority, view is stated in countless places
https://www.hamilton.edu/academics/centers/writing/seven-sins-of-writing/4
There are all sorts of opinions - and a style manual is exactly that, an opinion.
For Merriam Webster, the form changes under all sorts of circumstances (see ‘classical names’, to go back to our Jesus discussion):
https://www.merriam-webster.com/grammar/what-happens-to-names-when-we-make-them-plural-or-possessive
And when I asked my friendly household AI to show literary examples, it had this to say:
4. Proper nouns ending in s: In William Shakespeare’s “Henry VIII”, the character of Cardinal Wolsey is described as having “the Fothergills’ loyal support”.
These examples illustrate how possession is shown in nouns that end in s, whether singular, plural, compound, or proper. In each case, the possessive apostrophe is added to indicate ownership or relationship.
Further, the ‘Grammarbook.com’ tells us that there is no ‘right’ answer:
https://www.grammarbook.com/blog/apostrophes/apostrophes-with-words-ending-in-s/
As I said, I consider a lot of this to be opinion. I’ll stick with what I was taught back when even public education was still pretty decent; and what I’ve seen in a lifetime of reading accomplished English language writers.
It’s not superfluous. It’s only awkward if you accept that “they” is a singular pronoun and the “historical present tense” is not confusing.