It is routine for gasket makers and others to now suggest that ALL stressed bolts like head bolts should be changed, it is more of a guarantee their part will be successful. Besides that it sells more parts...............I notice that Felpro now calls for new bolts on engines I know for a fact don't need them.
The way you tell-
if final tightening is worded as a DEGREE OF ANGLE such as 90 degrees or 45 degrees or whatever, then yes, you need to change the bolts.
if final tighten is a TORQUE, or 44 ft.lbs. or 65 ft.lbs., etc. then bolts are reuseable provided nothing has happened to them that would warrant their being changed.
SPI seems to call for a last tighten of 1/4 turn so that is 90 degree angle, so yes, bolts need to change. They get stretched out of shape at first tightening, you can blow head gasket by using them again since they are already internally yielded (TTY, or 'torque to yield', the type of bolt).