I had a chance to try the T1.3 out for a while...
I was coming from a DT1990 as a daily driver, looking for a complimentary warmer headphone. The T1.3 are definitely warmer but still have a lot of detail, the moment I put them on I could hear they were high resolution. They already sounded good but curiosity got the better of me and I experimented with removing the foam pads, once removed to my ears they sound better - a neutral/warm tilt with a strong bass presence but more open, detailed and the recessed mids come forward. With the foam removed they actually sound fantastic, perhaps just lacking the airy 'sparkle' of the DT1990 which tend to give a bit more life to reverb trails, although in a direct comparison the DT1990's highs can come off a bit plastic sounding. It seems the DT1990 Balanced pads were used for the T1.3, switching to the DT1990 Analytical pads does bring some more air but also reduces the bass.
I understand Beyerdynamic were going for an uber cozy/warm sound signature but I can't help but feel they clipped the wings of the T1 driver in the process, as adding the foam back makes them feel restricted and not fulfilling their true potential. I hope Beyerdynamic tune a future T1 gen to a 'super DT1990 Balanced' style as the driver honestly sounds excellent.