^ How do you reach that conclusion? Black Tar Heroin is pretty widely used for injection and it is certainly not "the heroin version of opium" as that would be Kompot. There is much conjecture about how Black Tar Heroin is made and the process would likely vary atleast slightly but the opium is cleaned up, perhaps not to the standard that manufacture of other heroin forms requires, but it is not acetlated opium which was common in parts of Europe a few decades ago and referred to as Kompot.
I mean obviously black tar heroin is HELL on the veins but I don't think it is manufactured with the end users health in mind.
Another thing worth noting about Back Tar Heroin is the fact significant moisture is present in the product means it is much more likely to contain nasty bacteria. I forget the exact stats but I remember reading US West coast (tar) users were significantly more likely to have a heart disease that is usually contracted via injection of the bacteria versus East coast (#4 powder) users.
I don't even have to try tar to tell you that as illicit drugs go it is fucking gnarly shit, some people prefer the high from good tar to good powder but from the reading I have done most heroin users would much prefer the cleaner, and generally purer, powder version.