I scoured the manual as well, thus my curiosity was raised. Did this person see something in in the manual that I missed? Or he heard it from his bro who heard it from his bro?
I found this on the Line 6 forum - by extension they will probably set up something in IdeaScale for the DL4 MkII:
When another company makes a standalone looper, they have an entire team of engineers and developers devoting 18-24 months to that single product. Helix’s looper was always going to be utilitarian at best because no one can agree on what makes a world-class looper anyway. Look at the Headrush Looperboard—they spent gobs of time, money, and effort developing it, only to have 90% of looper geeks dismiss it outright because it didn’t have the exact workflow and feature set they’re accustomed to. Why would we want to follow them down that rabbit hole?
If you want Helix’s loops to sync to MIDI, visit IdeaScale and hope your request gets voted higher than the hundreds of other features and models that have been requested.