PBIRS Windows Authentication doesn't require AD prefix?

[Retriever]

I'm in the process of testing PBIRS as a potential switch from SSRS, and things seem to be going well. One of the shocking things that I've found is that seemingly, PBIRS doesn't require an AD\ prefix for native mode authentication. It just "knows" and I can enter only the username. SSRS has always required that we include the prefix. I'm using the same report server, just a different instance. 

Is this an actual feature of PBIRS? I've been looking around for some documentation of this difference, but can't find it. I can't tell if it's a fluke or a feature. If it's a feature, it's a really nice change. Remembering AD\ is one of our most common user issues with SSRS. Maybe there's some hidden setting in SSRS that I've just been missing for all of these years. 

Hopefully, someone can chime in that they see the same behavior and it's not just me and my test accounts. I keep trying to trip it up and it just seems to work fine. 

[teconsultant · Accepted solution]

We recently upgraded from SSRS 2014 to PBIRS May 2019 edition.  Some of our customers are on the same domain as the PBIRS server, and they don't require a login at all.  Chrome and Firefox browsers are able to login without the domain\username, and Internet Explorer/Edge browsers do require domain\username.