I disagree with the statement that when it is absolutely necessary to ask them to identify as male or female there should be a third option (or an empty line to

I disagree with the statement that when it is absolutely necessary to ask them to identify as male or female there should be a third option (or an empty line to write whatever). My hypothesis is that there are no valid reasons to ask them to state their identified gender, therefore the aforementioned forms are asking about sex and there are only 2 options, so no need for an empty line. I may be wrong. Other commenters wrote that - there are no valid reasons to ask for sex either, but they didn't provide an argument - there are more than 2 sexes, but didn't mention any other option.