i don't really believe it's a matter of "forgetting" - if you identify with those terms you are welcome to write them in, but gender descriptors are based on adding the most common write-ins for the year before.

it is not based on just requests but requires a certain subset of the people answering the survey to indicate it as their gender or else they would be having to list hundreds of self identifiers.
last year, the top identifers included:
butch: 2.5%
bigender: 2.5%
creature: 2.3%

so they were included this year.

if you had other feedback i would recommend providing it here https://www.gendercensus.com/ on the website, but since there's already a reason provided for this i felt it would be worth answering