Well, one of its constituents seems to have that effect.

First, green tea: EPIGALLOCATECHIN-3-GALLATE (EGCG), A GREEN TEA POLYPHENOL, SUPPRESSES HEPATIC GLUCONEOGENESIS THROUGH 5

And then, oolong tea: Unbound MEDLINE : Effects of oolong tea on gene expression of gluconeogenic enzymes in the mouse liver and in rat hepatoma H4IIE cell

This is interesting. For people who want to stay in deep ketosis, controlling excess gluconeogenesis that can actually take someone out of ketosis would be extremely useful.

Even for someone who isn't in ketosis, less gluconeogenesis means lower blood sugar, less insulin spike, and more protein able to be used for muscle building.

Finally, for someone fasting, less gluconeogenesis means more muscle spared. So what already small amount you are losing for glucose production becomes even less!