Grease on disc

I have noticed something peculiar in my NEC ND-2510A drive.

After formatting a CD-RW with Nero InCD, with verify, I can see concentric arcs (not full circles) towards the edge of the disc. First I thought these were scratch marks created by the lens or lens enclosure coming too close and touching the disc’s surface. However, closer examination showed these marks could be wiped out with a dry cloth, suggesting it was something like grease or some kind of a lubricant. Something with grease on it must be coming very close to the surface of the spinning disc to create these marks.

The funny thing is, this does not happen when I write to the CD-RW in the normal way (without InCD packet writing). I’ve erased and re-written the full capacity of the disk several times, without getting these marks. But the moment I do an InCD format, with verify, I get these marks.

It does not happen in DVD+R formatting (with verify) with InCD.

Has any one else experienced this? Why does it happen only for InCD formatting? Does packet writing bring the lens closer to the disc than in normal writing?

InCD format is greasy it ruins disc surface.

What is the difference between InCD formatting and normal writing? How can it ruine disc surface?