Obviously if my answer were 'no,' I wouldn't be writing these essays. However, this 'resource' essay won't argue the question; that'll be in SUPERHEROIC IDIOMS III. This post will deal only with the provenance of the term "focal character," though I plan to re-configure this term for my own purposes.
As one can see in the earlier Wiki citation, the term "focal character" traces back at least as far as a 1965 commercial writing-book, TECHNIQUES OF THE SELLING WRITER, by Dwight V Swain. It's certainly possible that Swain derived the term from another source, but I've found no evidence for it online, so for the time being I'll assume he invented the term. Unlike the "literary instructor" mentioned in my addenda to the TRAILS OF SUSPENSE essay, Swain was a published fiction-writer, though judging from online approbations the TECHNIQUES book seems to have been Swain's greatest claim to fame:
His first published story was "Henry Horn's Super Solvent", which appeared in Fantastic Adventures in 1941. He contributed stories in the science fiction, mystery, Western, and action adventure genres to a variety of pulp magazines. His first published book was The Transposed Man (1955), which appeared as Ace Double D-113, bound dos-à-dos with J.T. McIntosh's One in Three Hundred.-- from the Wiki entry.
Since I think I have that Ace Double, I may have read the Swain contribution, but I have no memory of it. In any case, Swain first introduces the term in Chapter 3 of TECHNIQUES, as a means of teaching the aspiring writer how to convey "feeling" through the characters to the putative reader. Swain's first important point in the chapter deals with the idea of "orientation:"
"...a story is essentially subjective, not objective. Consequently, it needs to be as strongly oriented as a person... a story is never really *about* anything. Always it concerns, instead, someone's *reactions* to what happens."
For Swain, the "focal character" is the character through which the reader perceives these reactions, and initially Swain seems to be talking about the commonplace notion of what is called variously the "protagonist," the "main character," or the "viewpoint character." However, Swain soon departs from this identification:
"Does this mean that the term 'focal character' is a synonym for 'hero?' Not unless Sammy Glick is a hero in Budd Schulberg's WHAT MAKES SAMMY RUN. Or Macbeth. Or Dracula. Or Elmer Gantry." Swain then adds that though readers are accustomed to focusing upon heroes who have "positive" aspects, "a focal character may prove the opposite, yet still intrigue us even as we loathe him."
Swain then also demonstrates cases in which the viewpoint character may be the same as the focal character (Huckleberry Finn, for one) and cases in which the two are separate. Of the examples he chooses for the latter, the most effective is that of Conan Doyle's Doctor Watson, who is the viewpoint character through which the reader perceives the true focus of Doyle's story, who is of course Sherlock Holmes.
This insight, however, isn't followed very far, for on average through the remainder of the book Swain tends to talk about his hypothetical focal characters as if they were, like the example of Huck Finn, identical with viewpoint characters. Clearly, Swain's only reason for coining the term was to clarify the options open to any aspiring writers: that one could choose to make the focal character a figure seen through the eyes of viewpoint characters, as in his most pertinent (IMO) examples, Bram Stoker's Dracula and Arthur Conan Doyle's Sherlock Holmes. I'll touch on these examples in AGAIN SUPERHEROIC IDIOMS PART 3, and how a "viewpoint character" who is more an observer or catalyst than a primary focus makes it possible for something non-human to be the story's focus, the true "star of the show."
In closing I will remark that as a result of my online searches I learned that another author, narratologist Gerard Gennette, also made use of the term "focal character" within the scope of a more advanced academic theory. However, Gennette's usage does not seem to have seen print in book-form prior to 1965, and even if it had, I find it improbable that Swain, by all indications a simple formula-writer, would have encountered Gennette in any form. Whatever the merits of Gennette's narratological system, they don't for the present concern my mediations on the question of heroes and focus characters.