Plus the 12 speed di2 components use a different wiring, so you need an adaptor, which Shimano provide, but I don't think everything works out the box, because some 11 speed components haven't had updated firmware to work with 12 speed yet.
No 11 speed components have gotten a 12 speed compatibility update (or are likely to get one) except the TT-specific shifters.
@grams started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
Plus the 12 speed di2 components use a different wiring, so you need an adaptor, which Shimano provide, but I don't think everything works out the box, because some 11 speed components haven't had updated firmware to work with 12 speed yet.