There are at least 7 different genes that produce a wrapped belly. Any chin with a wrapped belly is called ebony, regardless of which gene caused the belly to be wrapped. Charcoal (bb) is one of those genes, it is recessive so any charcoal chin is a **** eb, but charcoals can range in shade from light to extra dark. Thus, a light charcoal is genetically a **** eb, but is not every hair shiny black.
Some of the genes that cause wrapped bellies are recessive (like the charcoal), some of them are dominant. Some are thought to be accumulative, but I'm not entirely sure it's actually accumulating or a hybridization of two or more of the genes that cause the wrapped belly.
Back in the day, some ranchers threw any ebony into their lines trying to darken their herd because darker pelts were in demand. This resulted in a genetic mess and there are no longer any pure strains of ebony in the US, and no one really trying to separate them (that I know of). You can tell your chin is an ebony because its belly is wrapped, but you don't know what combination of the 7 known genes for wrapping caused it.
Using "**** Ebony" to mean "every hair shiny black" and "Hetero Ebony" to mean anything else is common usage, but it is inaccurate and misleading. Ebony is not any one single gene.