A very common concern, but overblown in my experience. If you notice, I never actually said "judge the candidate's presentation skills" (or anything of the sort) in why I think this process is great. The presenation is really just level-setting; the candidate gets to set the topic and give sufficient context for a conversation to occur. The presentation is at most the first 15 minutes out of a ~3 hour in-person interview process. That's how little it matters.
It's the Q&A and subsequent discussions that matter.