Fetch custom field guide instructions not matching

ERPNext
,
1

I’m trying to follow this guide:
https://frappeframework.com/docs/user/en/guides/app-development/fetch-custom-field-value-from-master-to-all-related-transactions

However, step #2 is not possible. In my “Fetch From” field, I am unable to enter “supplier.gstin” like in the guide instructions and only get to choose from the drop down list and “supplier.gstin” is not available. Should the guide instructions be updated?

Fetch From 1
Fetch From 13834×1224 157 KB

Fetch From
Fetch From3819×1697 315 KB

2

I found a working video guide from Fetch From Doc_type - #4 by NCP
I wished the written guide was updated to the correct instructions.