I guess he means the retpoline. On the 6502 there is no indirect jump instruction, so you need such tricks just to achieve an indirect jump at all.

There's an indirect jump instruction. It's not very good though, and has a notorious bug with addresses ending in 0xFF.

Gah, you're right. Guess my memory is fading. There is indirect JMP, but no indirect JSR or indirect branches. And the indirect JMP as you say is not very useful.

I think it means they're tricks for better performance when you _don't_ have speculative execution.

Speculative execution is as old as branch prediction, which is very, very old.