Geometric mean is commonly used in benchmarks when the workloads consists of queries that have large (often orders of magnitude) differences in runtime.

Consider 4 queries. Two run for 1sec, and the other two 1000sec. If we look at arithmetic mean, then we are really only taking into account the large queries. But improving geometric mean would require improving all queries.

Note that I'm on the opposite side (Databricks cofounder here), so when I say that Snowflake didn't make a mistake here, you should trust me :)