I bet a bunch of people would have a hard time proving their hours.
Phone calls are easy to prove. So are purchases. A guest on Avery Carl’s podcast said that people who try to recreate their time logs get in trouble because their electronic paper trail contradicts them.
Stuff like everyday clerical tasks where there is no paper trail are tough to prove, but the IRS can’t easily disprove them either. Although if it looks wildly exaggerated for small tasks it is likely to be denied.