I wouldn't say it's particularly inefficient...just taking a look at the format spec, if you were just taking straight output it would be a json blob with a hea

I wouldn't say it's particularly inefficient...just taking a look at the format spec, if you were just taking straight output it would be a json blob with a header containing metadata and just a bunch of raw "o" events with line by line raw data. Certainly not as efficient as just outputting the STDOUT into a line-delimited format, but not inordinately larger.