You can say that about anything. You can't prove there is not a tooth fairy, lol. When Berry Gordy ran Motown, he always told his acts they sold less than they really did so they didn't have to pay them as much. Motown also didn't report sales to the RIAA until stuff released after around 1984 or 85. When James Brown was signed to King, they did the same thing. Some other labels during that period bought thousands of their own records to spike the charts. Then there's that debate about the Eagles' Their Greatest Hits (1971-1975) album. Some sales aren't counted, like those from record clubs, cut outs, mom & pop stores, stolen albums, or ones that are broken in shipment. Soundscan isn't foolproof either, and it only came about in the 90s. So record companies have no idea how much something has sold, and just put out numbers for PR reasons.