It's been a thing since its introduction that Spirit Bomb can only be used by pure hearted and can't hurt them.
Super Saiyan isn't pure hearted since it's literally anger and vengeance fueled transformation.
In Toei's Super 13 movie they decided to use this concept where Super Saiyan Goku formed the Spirit Bomb but couldn't throw it since it would backfire on him, so he instead just absorbed all that energy into himself for a temporary powerup to kill Super 13.
Then Toei repeated this shit with Trunks and the Spirit Sword.
And then they SORT OF repeated it during Tournament of Power where Goku gets it thrown back at him and it explodes in his face but he instead absorbs all the energy and basically temporarily forces himself into UI.