I understand all that but it stills doesn't explain why the link says one thing, even hovering over the link it displays http://www.borisfx.com/download_files/BCCOFX_2021_5.exe. When I click on the link I get Continuum_2021.5_OFX_Hosts_14_5_3_Windows.exe to download which I have already installed. So, I'm confused.
You have to go through the installation following what the video says. You will not get "only" Optical Diffusion to download. It will be the entire Continuum complete.