Suppose that you have a spreadsheet with cells A2:C3 containing some numbers and a conditional format defined on that range. Next do one the following in order:
a) Select the range. Using the black box in the lower-right of C3, expand the range down one row. The data and conditional formatting will both be expanded.
b) Select the entire expanded range (or any two of the rows). Copy and paste it immediately underneath. A new conditional formatting rule is created for the copied cells.
c) Select only the last row. Copy and paste to a new row. Now three separate rules are created, one for each cell.
(I have also had a situation where copying and pasting created thousands of identical rules on the same range, but I am not able to reproduce that.)
I can see where it might be desirable to distinguish between stretching and copying (though personally I’d prefer if it didn’t), but not why it would make a difference whether I was copying one row or multiple rows. Is this something where we should request consistency, and if so, in what way?
(Slghtly edited by @Lupp for better readability.)