>>7811277>the fact that they permanently replaced the original set of Mata masksBingo. It's not temporary transformation, as far as G1 goes this is how they (sans Tahu) are stuck looking.
Despite that, the Mata have always stayed as the real faces of the franchise, and thankfully Lego understood that for G2 (one thing they did right, at least). Even the Uniters, which are meant to take after the Nuva, still evoke the Mata quite a bit (Lewa especially).