They're objective in that people agree on them. All programmers would say that a more efficient or shorter or more reusable piece of code is better, notwithstanding other tradeoffs that it makes.
My use of "objective" is to distinguish from subjective criteria that people often don't agree on, like "it's more idiomatic" or "it's simpler."
Whilst the measures may be objective, the ordering of them is not. That's quite subjective.
Personally, a shorter piece of code is only better if it maintains the clarity of the longer that it is replacing - assuming all things being equal. Code is always a trade-off.
My use of "objective" is to distinguish from subjective criteria that people often don't agree on, like "it's more idiomatic" or "it's simpler."