You are removing branches, and adding slightly less clear code to do it. If this resulted in faster or cleaner code you would already be doing it. So the OP’s point holds: if these security holes are fixed at the CPU level, there will still be a generation of software compiled with these mitigation’s in and no way for a user on a newer CPU to disable them.

EDIT: I just wanted to clarify here that I did not mean “all branches” just some of them, hence the name of the technique which is “branchless security” (which is a really good piece of engineering). The frustration is basically we have to bake in CPU model specific mitigation’s into binaries. You can of course patch it out, but the affected CPUs will in theory be in the wild for a long time to come even once corrected ones are released.