How did it go through peer review without a comparison with ClickHouse?

> Our analysis shows that the Compact layout performs better when Null ratio is high and the Placeholder layout is better when the Null ratio is low or the data is serial-correlated.

ClickHouse uses a placeholder value with a separate stream with NULL-masks, and additionally, it has the Sparse column format, which is named Compact in the paper (but currently, the Sparse format applies to encode default values more efficiently rather than NULL values).