It's not relative vs absolute, no. Jumps and call instructions have been using PC-relative values right from the start. You might be thinking of RIP-relative ad

It's not relative vs absolute, no. Jumps and call instructions have been using PC-relative values right from the start. You might be thinking of RIP-relative addressing, which is useful in PIC to access globals. The problem is that there is no way to know at compile time the position of an instruction relative to its target. Non-PI code handles this by having the linker update the relevant constants in the machine code. PI code has to function without modification, so it must indirect through a global table. It's this indirection that causes the speed hit. On the other hand, PI code benefits from the ability to share code pages, so it can be faster in some circumstances.