Brown, 'Titian and Bellini' pp. 57-67 discusses the evidence for the relationship between the two painters. According to Vasari, Titian abandoned Giovanni Bellini as a teacher because of his harsh and laboured style, and turned instead to Giorgione ( Vasari, Le Vite, Testo VI.155). According to Dolce's Aretino of 1557 Titian was first placed with Sebastiano Zuccato, then moved to Gentile Bellini, but looking for more 'perfection' transferred to Gentile's brother Giovanni, before he finally moved to work with Giorgione.
Ruskin seems here to be challenging that account of the relationship between Titian and Bellini and the account given by Reynolds on Titian in Discourse Eleven where Reynolds argues that Titian knew how to 'mark the general image and character of whatever he attempted; and produced by this alone, a truer representation than his master Giovanni Bellino, or any of his predecessors, who finished every hair' ( Reynolds, Discourses, p. 195).