I think Muftak's "sloppy writing" comment was in reference to Han being inconsistent in terms of Alderaan's destruction. At first he acknowledges it's been destroyed but a second later he calls it impossible.
In technical terms, it's a 'meteor' when it enters an atmosphere. Before that, it's termed as a 'meteoroid'. But since Han mentions 'asteroid' immediately after, the two words (meteoroid-asteroid) spoken almost back-to-back might sound a bit awkward. Maybe Lucas knew this,....who knows, but I REALLY doubt the Han took the Falcon that close to Alderaan's atmosphere for the term to be correct. o-o
I don't necessarily see this as being inconsistent, though. Han knows Alderaan has been destroyed, what he thinks is "impossible" is that the Empire was responsible, based on his knowledge of their capabilities.