Power BI Measure without relationship between tables

Hi,

I have a problem with a measure I found in a customer's report because it works but I don't understand how. Basically we have two tables, one fact table and one dimension table, the measure performs a count of the rows of the fact table under some specific filters. The problem is it uses a column of the dimension table in order to filter, but there is no active relationship between these two tables and it is not specified inside the DAX formula. There is an inactive relationship between these two tables but it a many to many relationship with no real usage. I don't understand how the results that the measure gives are correct and actually filtered without an explicit nor implicit relationship. 

Thank you in advance