I see the argument that C on an Intel CPU is not low level enough for this person. On arm cortex m and r series CPUs, it’s low enough. (I don’t know enough about the A series to say this).
The gripe is mostly that there’s microcode in the pipeline for branch predictions and that takes the control away from them. If you want to own that control, You’re going to lose on speed.
Should you be bothered? Generally, No. If you are, there are CPU options out there with smaller pipelines and much less predictions going on. But don’t expect them to compete in the same arena as an application class CPU. (Intel, AMD, Arm A series likely)