The mistake wasn’t Jürgen’s, it was ours (Microsoft’s)
Some of the MIDI bits escaped the pen and got into 25h2. Not sure how, but we recently did a ton of branch changes, so I suspect a PR went into the wrong location. Now, the bits aren’t enabled by default, so unless you plug in a MIDI 2.0 UMP device, they won’t get in your way. If you do plug in a UMP device (like the Komplete Kontrol in MIDI 2.0 mode, or an Iridium/Quantum in MIDI 2.0 mode, etc.) just reboot and it will get reassigned to the correct (older) driver.
The MIDI bits in that release are a couple months old. But importantly, they aren’t wired through to the MIDI 1.0 APIs, so you won’t see those devices in WinRT MIDI 1.0 or WinMM MIDI 1.0. They also don’t have the final device names, so if used, would break just about every DJ app/device out there. (Apps like Rekordbox don’t let the user pick a MIDI input, they discover known devices by name)
Sorry for the confusion there. I asked Jürgen to pin a comment from me in the video so others will know. There’s a ton of interest in this, more than I thought, as I found out this week 
As to the benefits, it’s much more than just MIDI 2.0.
- Multiclient MIDI 1.0
- Built-in loopback endpoints
- Ability to rename MIDI 1.0 ports
- Dedicated MIDI Settings app for configuring MIDI
And for apps using the new SDK, they also get timestamped messages, ability to send/receive multiple messages at a time in a block, virtual MIDI device app-to-app MIDI support, and more.
We’re fixing a couple last-minute (really, they came up just as we were ok’ing the release) bugs discovered by partners. Both are critical to fix before we enable this for everyone. Those bugs mean we won’t hit our November release date, so will be early next year instead.
Pete
Microsoft