streaming seems broken when using custom command

[dwelle]

When using the default command (convert), streams work as documented:

const gm = require('gm');
const fs = require('fs');

gm('a.jpg')
    .in('-resize', '3000x>')
    .stream()
    .pipe(fs.createWriteStream('./out/a.jpg'))
    .on('error', (err) => console.error(err))
    .on('close', console.log('done'));

But, when using custom command, e.g. mogrify, they don't seem to:

const gm = require('gm');
const fs = require('fs');

gm('a.jpg')
    .command('mogrify')
    .in('-resize', '3000x>')
    .stream()
    .pipe(fs.createWriteStream('./out/a.jpg'))
    .on('error', (err) => console.error(err))
    .on('close', console.log('done'));

Any ideas?

v1.23.1