Constant PIO_DIST_ABI_VERSION 

pub const PIO_DIST_ABI_VERSION: u32 = 1;

Frozen at 1 and no longer meaningful. It existed to absorb distribution volatility, but that volatility lives in the BMOPF schema, which changes a reader, a writer and an emitted token, and no C signature. One shared object carrying two compatibility promises is a thing no mature C library does.

The symbol stays because PowerIO.jl gates thirteen distribution call sites on resolving it, and removing it would break every distribution call on a library that fully supports distribution. Foreign schema drift is reported at runtime by pio_build_info instead, which can express “BMOPF 0.2 but not 0.3”; an integer checked once at load cannot.