fixed vs include

I was going thru below link when it mentioned that

FIXED LOD would result in wrong values, unless you build a separate calculation for each of the options just before exclude. I am not sure why would it result in inaccurate computation

https://www.thedataschool.co.uk/hanna-nykowska/tableau-lods-include-and-exclude

If i include multiple dimensions, the syntax is as below and would work as fine as include:

{FIXED [dimension1], [dimension2], [dimension3]:....]}

Thanks