Why is cis/trans stereoinversion with Li+(THF)4 migration across the phenyl ring of α-lithiostyrene accelerated by two ortho-methyl groups?

Why is cis/trans stereoinversion with Li+(THF)4 migration across the phenyl ring of α-lithiostyrene accelerated by two ortho-methyl groups?

Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Tetrahedron - Volume 74, Issue 14, 5 April 2018, Pages 1621-1631

Rudolf Knorr, Ernst Lattke, Jakob Ruhdorfer, Kathrin Ferchland, Ulrich von Roman,