As jacobr1 pointed out, it's a disadvantage of metal-gate transistors, not an advantage. Silicon-gate transistors are entirely better than metal-gate transistors. (Except now metal-gate transistors are coming back for high performance, using "high-k" metals like hafnium. But these are completely different from 1970s-era metal-gate transistors.)

For your other question, the visible metal trace on top of the IC package is a common thing with ceramic packages. I think the purpose was to ground the metal lid of the IC to protect against noise, static, etc.