Phil Seamark lays out the consequences of a change:
If you have ever watched a model with row-level security run beautifully for months and then quietly fall off a cliff, this one is for you. Nothing in the model changed. You did not touch the security rules. One table just grew past a line you could not see, and every query under that role started doing a great deal more work than it used to.
That line just moved, and it moved in your favour. Here is what it is and why it sits where it does.
Click through to learn more about how Power BI handles row-level security predicate matching.