Why create a new table which is a copy of dim_Date table ?
Two related questions here :
#1 from about 6:40 in the video you showed us how to create a new table to set up the active relationship, as mentioned in the video that creating a new table consumes memory, is it better to just keep the original two tables/ queries) and have one active relationship and one inactive relationship in your case ? and to avoid writing M codes to create a new table. It seems to me that an inactive relationship from the original two queries works as well.
#2 Does active relationship take "priority" over inactive relationship ? looks like inactive relationship in this lecture still serves the function of generating the proper report(chart).
The best scenario is to have one dim_Date table with active and inactive relationships. The ones that are active always take priority over the inactive ones, because the only way to make the inactive relationships work is by using the USERELATIONSHIP DAX function. Having two dim_Date tables solves our problem as well, but creates and extra calendar table for your model to manage.