Seriously, this video, literally and in particular has been haunting me for YEARS now and is one of the things which I cannot stand. It is so plausible and so very easy to get wrong.
I swear the double slit experiment is one of the worst offenders for getting people to peddle around nonsense about the observer effect and some metaphysical gymnastics about how consciousness actually creates reality and you end up with people saying lots and lots of words which they don't even understand but are entirely convinced that they do. Even the name "observer effect" is a poor choice of words which we are now stuck with because it is so ubiquitous, but it is actually interpreted wrong most of the time, because it is not even about the observer, it is about the effect and it has been shown by experiments that consciousness is not required in the measurement but people regularly flout this over and over and have been doing so for years. I've fought against this very same video probably hundreds of times to no avail.