I have that one too!
I'm baffled too, we bought this one a couple years ago and I kinda suspect the shape of the base isn't incorporating air properly into the emulsion. It's also an oval shape instead of most round immersion blenders I've used so I don't think that's helping:
https://smile.amazon.com/Breville-BSB510XL-Control-Immersion-Blender/dp/B004RF7QJW/
I had a few more close looks at the video and I think he's using this All-clad model:
https://smile.amazon.com/gp/product/B007R2E47Y/
I don't think wattage is everything, but it's interesting that the All-clad is a 600 watt model while the Breville is only 280 watts. Thanks for listening to me rant, props to kenji though for upping my cooking game in all sorts of areas since the pandemic started...