It looks like LG updated the user guide for this TV, and it states that 8K 60hz 4:4:4 is now supported. Was this change from a firmware update, and can you confirm that it now works? Thanks!
http://kr.eguide.lgappstv.com/manual/w20_mr2/atsc/Contents/settings/picture/deepcolor_k_u_b_01/enga/w50__settings__picture__deepcolor_k_u_b_01__enga.html