No it isn't. Not defamatory at all.
I don't know if the Reg journalist did due diligence on the term before using it, but sinecure to describe an advisory or chair role is actually quite correct.
First, it relates to catholic Christianity, not Judaism.
Second, it just means "without a parish" from the Latin sine without and cure, a word meaning responsibility but, in the context of sinecure, meaning "a parish". Thus being a canon of a cathedral was usually a sinecure because, although cathedral clergy advised the Dean and had various admin jobs, they didn't have a parish to attend to. Some clergy, of course, had parishes which they then let out to a vicar or curate on a salary while they enjoyed the tithes.
The glass is for the subed for using exactly the correct word.