BYU had the starters to play M2M in the secondary last year, but the GFGH offense made it really difficult on the defense in terms of total number of plays. BYU's 2016 offense will huddle and provide more recovery time for the D on the sidelines. Obviously if other teams GFGH, it can strain the D a bit, but it is not compounded by BYU's O potentially being on the field for a minute or two only.
The biggest issue I heard about the D and the GFGH was depth because they had to be on the field for so many more plays.