They started playing Scream on the radio 2 weeks before they were supposed to. I think that would impact sales.
I just mentioned that You Are Not Alone
was played before it was an actual single and I also did not hear Scream
on Top 40 that much. You Are Not Alone
was the big hit in the USA from that album, and being played early didn't hurt its popularity. The singles chart was based on both radio airplay & sales of physical singles. If a song did not get the heavy airplay, it would affect it on the chart. Also in the USA back then radio (usually not on Top 40 though) would play album tracks. AOR & college radio stations would sometimes play an entire album at once or a few songs in a row by the same artist. There was a radio program in the 1980s that came on every Sunday morning called Breakfast With The Beatles
that would play their unreleased songs, group & solo. I guess they were from bootlegs. So I don't know how any leaks was supposed to hurt much, especially just 1 radio station in 1 city. There was/is thousands of different radio stations all over the USA with all kinds of formats (R&B, Top 40, gospel, adult contemporary, contemporary Christian, dance, AOR, country, smooth jazz, easy listening, alternative rock, oldies, classic rock, hip hop, Adult R&B, etc). Some larger cities have 2 to 4 different radio stations with the same music format.