At 5:30, you can see clearly that the "table saw track" at the back of the workbench (aluminum rails on which the fence is mounted) is sticking out further than the space that is has been created for the base plate with miter tracks to be inserted:
When everything is put together like this, the original tabel saw fence cannot be moved to the most left position anymore.
Of course you have the sliding carriage to use, however, I can think of situations you would like to just use the original table saw fence to make a quick cut or something.
In that case there should be a cut-out in the base plate (underneath the sliding carriage) to make sure the travel of the table saw fence is not limited by bumping into the base plate with miter tracks mounted.
Was this a decision you made to not being able to use the complete travel of the original table saw fence?