Jay, I look at this as a good way to not have to take my laptop to a measurement.
I look at all courses on MapMyRun.com before I do anything. Once I look at it, I know which way I will measure it, whether I need a turnaround, or not, and all the variables. So it is no problem to make an adjusted sheet on my desktop, and put an updated worksheet on the phone.
The point is not to remove all need for another computer. Rather, the point is to load a spreadsheet onto my phone for use in the field. If I have to customize the pared-down spreadsheet, I do that at home.
I also don't keep it on the whole time. I put my start clicks into the spreadsheet, and then I copy to a note pad my splits I need. If I had a mount for the phone, I could keep in on, but what's the point? Maybe a transposition error, but I copy from my laptop onto a note pad, anyway.