While Sprang also drew Batman according to the Bob Kane style, I imagine that a lot of older readers would have learned to identify him as the "good" Batman artist (like Carl Barks on Donald Duck or Dan DeCarlo on Archie). Whereas, for most readers, Sheldon Moldoff was Bob Kane--just as Lew Schwartz had been Bob Kane before that. Those ghosts disappeared into the style and didn't do a lot to stand out in the way that Dick Sprang stood out.
And there were other artists like Jack Burnley, Jim Mooney and Win Mortimer who drew Batman and Robin according to the Bob Kane model, but otherwise didn't alter their style . So a Jim Mooney Batman story is not that different from a Jim Mooney Supergirl story and you can easily tell that the same artist worked on both.
Now when I look at a Moldoff Batman story, I can spot his touch (nine times out of ten)--but it's never as obvious as Sprang.