Difference between '~' and 'default' for tag path?

Noticed some weird behavior when dragging tags to the easy chart – it sets the tag path to ‘[~]tag_name’ instead of ‘[default]tag_name’.

I’m allowing the user to save custom trends, so I’m later referencing the tag paths configured in the chart, but the scripting functions don’t seem to like the [~] tag path (system.tag.exists() returns false).

Since I’m just using the default provider, I can just manually modify the tag path when referencing it, but just curious as to what the point of the [~] in the tag path is and why I need to work around it in this way.