This is the take of an undergraduate that's studed Chinese history so I'm not perfect in my knowledge.

It's impossible that ethnic Greeks built it since Sima Qian's (145 - 90 CE) Records of the Grand Historian does not mention foreigners being hired to do it. But it's not impossible ether that there may have been subtle Greek influence. After all, artists of the Greco-Bactrian Kingdom (250 - 125 BCE) influenced Buddhist art. You can still see some of this influence in Chinese Buddha statues that have carried on remnants of artistic tropes of that era of Greco-Buddhist interaction. But no major piece of evidence has come forward yet with regards to the Terracotta Army. DNA tests of Xinjiang province have led some to claim that "Europeans" intermingled with Han settlers there but this is not conclusive evidence. Indo-Europeans were once an ethnic group in the region but this does not mean they were the same as the Greeks. Also, to my knowledge, materials found dating back to the region's Indo-Europeans have a different art style from Ancient Greece. Others have pointed to the jump from smaller figurine sculpting to life sized sculpting as evidence since before the Army, Han culture had no tradition of life sized sculpting. But I would ask, is this really impossible that just because the Chinese lacked such a tradition that it MUST mean that they had outside help or influence? I find this kind of reasoning weak on its own without more evidence to support. After all, such reasoning can be applied to innovations throughout history. Other than that I'm not familiar with other arguments for this theory.

To me the evidence for this Greek influence on the Terracotta Army doesn't seem to be there but I wouldn't rule it our entirely. It's just a low probability unless more evidence comes forward.