Default value not being submitted using %get[key] on disabled or hidden fields

I'm building a site locally using webform 5.x2.0-beta3 and have been able to pre-populate my form fields with queries from the URL using %get[key]. On all editable form fields the variables print out just fine and I can see them in the results of the forms. But when using %get[key] on a hidden field, or a text field that is disabled from editing, the values do not show up in the results, those fields are just blank.

When viewing the source before the form is submitted I can see the correct values in the source code of the specified hidden fields, but after submission they are still blank. The correct values also show up in disabled text fields but are blank after submission as well. I tried setting the default values of those fields to just plain text like "default value" and it showed up just fine in the results.