[dba-Tech] Interesting Excel problem

The Edit setting, 

Extend data range formats and formulas

Two columns are formatted with a back fill color. One contains a time value the other contains a formula that returns a time value. Both columns have a custom time format (h:mm). 

When I add a new row, Excel extends the formula and back fill format for the column that contains the formula. It does _not_ extend the back fill format for the column that contains just a time value and the back fill format. 

I'm not sure why -- shouldn't it extend the back fill format for both columns? Perhaps I misunderstand how this particular feature works -- I expect it to extend formatting as well as formulas, but perhaps it only extends formatting for a formula? It doesn't say "formats with formulas" it says "formats and formulas." I tried a few other formats and it doesn't extend any formatting at all, unless there's a formula in the column. 

Susan H.