The Parquet writer always adds the BIT_PACKED and RLE encodings even though (I'm pretty sure) we never write out the BIT_PACKED encoding for rep or def levels. The BIT_PACKED encoding is deprecated according to the Parquet specification: https://github.com/Parquet/parquet-format/blob/master/Encodings.md and it is not clear that Impala can even read it correctly:
One way of seeing that Impala claims to need the BIT_PACKED encoding is to write a parquet file with Impala then inspect it with parquet-tool.
BIT_PACKED is never written by Impala's parquet writer - the definition levels are always written using an RleEncoder and reported as Encoding::RLE. Weirdly, the repetition levels are reported as "BIT_PACKED", but this encoding has no effect since we don't actually write out repetition levels.