Heat Pump - emergency electric strips - how controlled?
Being that you are only talking about 1 degree difference I would think it is possible that the tstat began the heating cycle while the outdoor temp was at 35 and rose to 36 mid cycle.  Also, it's been 10+ years since I have been involved with Goodman, but they used to have a timer on the defrost control board so that if the unit ran for 30 ~ 120 minutes it would shutdown the heatpump and bring on the backup heat strip. The timing is set via a small dial on the defrost control board.  I believe that the default value is 90.  At 36° ambient temp, depending on the outdoor relative humidity, your heatpump certainly could have been running long enough to exceed that time.