Seems to have been completely missed by the YouTubers (perhaps because no one cares about mechanical any more?) but a mechanical GRT13 groupset was visible in Trace Velo's video from Shanghai Bike Show.
L-Twoo? If so, hopefully it comes with a better RD than the one they send with their 11 and 12-speed stuff.
I finally just up and replaced the RX (12-speed) rear derailleur with 105 and it's a night and day difference. Really weird to have a b-screw that actually does something and springs that aren't made of wet noodles. For anyone on a budget, the 11-speed 105 rear derailleur is $15 less and works perfectly with 12-speed: