There are a couple of ways to argue that...
Is the real Brandywine the Johnson and Stokes commercial variety named brandywine from the 1890s?, and is that the Landis Valley "Red Brandywine" handed down by the Amish?
When people talk about Brandywine, the tomato that made heirlooms popular, they are talking about pink potatoleaf "Brandywine" from the Sudduth family, so that is the real Brandywine from that standpoint, if not from a historical "where did the name come from" point of view. I would say that the 'new' Red Brandywine, and Red Brandywine potatoleaf are "fake" Red Brandywines, but at this point more people are growing them than they are the Landis Valley strain.
Because all of the other ones originated as crosses, having brandywine in the name is pretty much meaningless except from an advertizing point of view. Throwing the term "Amish" at anything with brandywine in the name is also a popular thing to due to sell more seeds. "Brandywine" is not Amish, "Red Brandywine (Landis Valley strain)" is. Heriloom Seeds seed company introduced Red Brandywine and still leaves off (Landis Valley strain) from the name, simply stating that theirs is the original Red Brandywine. Note that they also list Brandywine, Pink, and Brandywine (Sudduths strain) indicating that they bought their "Brandywine" seeds from two different sources, only one of which could be traced back to Ken Ettinger.
To get the story on True Black Brandywine go here https://rareseeds.com/seeds/Tomatoes-Purple
Why are there different strains of Brandywine (pink potatoleaf)? because Dorris Sudduth Hill gave seed to Ben Quisenberry, who grew it, sold seeds, and distributed seeds through Seed Saver's Exchange. Quisenberry grew many other tomatoes as well, such as Stump of the World, and so some of the Brandywine seed was crossed when it got to other people. The seed companies got their starter seeds from these other people, and so these strains are differ in quality. One person who got seeds from Quisenberry was Ken Ettlinger of the Long Island Seed and Plant company. Ettlinger grew out Brandywine for several years and stabilized it for high quality. This is the stable seed source that eventually was named "Sudduth's strain"
A contrasting parallel to this story (can I say contrasting parallel???) is that of Cherokee Purple. There is an older variety named "Cherokee", which is red, unrelated, unpopular, and more or less unknown, but if tables had been turned with Cherokee being the famous one, then people might be dropping the "Purple" when talking about 'Cherokee Purple' the way they do when talking about 'Red Brandywine'.
'Cherokee Chocolate', and 'Cherokee Green' are actual color variants of Cherokee Purple caused by mutation in two specific color genes, not the result of crossing it with other tomatoes, which would mix up all the genes(as is the case with the Yellow, purple, black and anything else with brandywine in the name). Cherokee Purple has the green flesh gene mutation (gf) which gives it a dusky color when combined with the normal red flesh gene (making it a "black" tomato). It also has clear skin making it look purplish. Cherokee Chocolate developed a mutation in the clear skin gene (y) turning the skin from clear to yellow (so it looks brownish), and Cherokee Green is a Cherokee Chocolate that mutated the red flesh gene to the yellow flesh mutation (r), turning off the red and leaving just green. Green flesh (gf) plus yellow flesh (r) gives you a green when ripe tomato. Cherokee Green still has the yellow skin mutation so it gets an amber hue when ripe. Plant size and structure, along with fruiting habit are the same or all three, and although the flavor differs slightly all are exceptional.
Note, the difference between a pink and a red tomato is simply the color of the skin, clear vs yellow, from that single gene.