I don't know what encode_json() does to "fill in" $typehint_raws, but it doesn't seem that it can be of much consequence since $typehint_raws goes out of scope with the return statement that immediately follows the subroutine call.

Not sure why you say that. I've run the code dozens of times, on multiple tables and searches. Not just getting back the proper output, but my server error log shows no errors.

still asking because I don't want to get bit in the rear later on.