The documentation is oddly worded about the check range.
What it seems to actually do (and what we look for when checking the doc) is how to selectively cook the null but take into account multisample changes. And thats what check range does but the way its worded it seems to mean that it looks for sample number changes only.
It could also be mentionned in the selective cook portion that unless check range is selected, the null with look for changes only in the first sample. That would save a few new users headaches
checkrange - Recook when the Null CHOP channel range changes.