I'm surprised you didn't have any problems, the product description clearly states that pin 3 is grounded. A few posts back Mike from Bryston issued a warning to float pin 3 if using the rear XLR outputs for SE applications. Anyway, i'm glad nothing happened to your amp!
It turns out every XLR to RCA adapter i've looked up has pin 3 grounded. I'm not taking any chances, i will cut off the connection between pins 1&3 just to be safe.
On an unrelated note, I found different circuit topologies when doing a search, notice the four large capacitors in the attached photo? This is different than the photos a few posts back showing the amps on the test bench at the factory, I wonder when this change happened...