Soft head problem is caused by your pelvic floor muscles being too tight and not allowing blood flow in. Doing kegels makes it worse by causing more tightness in those muscles. For people like me who has a tendency to naturally clench the pelvic floor muscles, doing kegels is not helpful.
I found this it as when I first started dabbling in PE, I thought kegelling was good so did a lot of it only to find erection got worse. I think they call this problem “flaccid hard” so I started reading into it and now do reverse kegels or ballooning instead.