Strict projection isn't required and wasn't implemented for several of the partitioning transformations. When strict projection isn't implemented (the projectStrict method returns null) Iceberg will fall back to a safe implementation. For example, residual evaluation will not remove predicates because they cannot be guaranteed to be true, and deletes can't determine that all values in a file match so the file can't be deleted (deletes usually fall back to min/max metrics evaluation).

Implementing strict projection for all transforms where possible will help query efficiency, will make deletes faster, etc.