The "emdash" between the title parts in both Chinese and English are uneven (see "red").
The part for equivalence: no space needed between "ISO 1231" and ",", no space needed between "," and "MOD") (no space is needed after a Chinese comma -- maybe this should be a general "script=zh" concern)
In GB/T 1.1 the "Part" title part does not come with an emdash, but a space is used to separate. See further below.
The "Part" section of "第1部: " should be "第1部分:" (again, no whitespace after Chinese colon)
No em-dash in Chinese title; removed spaces in English title.
This was not a spacing issue, but a Liquid template whitespace issue. (Of course, so long as the identicality clause is in SimSun, it will look like there's extra space after the comma anyway.)
Current:
Original:
Other examples of title part "Part":