Encrypting a folder

I'm familiar with bitlocker, having been using it for a while, but I am looking at just encrypting a folder instead. But I just don't understand the options it's giving me.

When I right-click a folder > properties > advanced > [x] encrypt contents to secure data > OK < apply > ...

I get:

() apply changes to this folder
() apply changes to this folder, sub-folder and files.

This doesn't make sense to me at all, if I encrypt a folder then the whole folder, everything within it is encrypted, then why should I be given these options, how can I have a folder encrypted and files within that folder unencrypted, that seems stupid to me, it doesn't make sense at all.

Can anybody explain why these options exist and how can I simply encrypt a folder?

When you select "apply changes to this folder, sub-folder and files," Windows will encrypt the entire contents of the folder, including all files and subfolders. All new files and folders added within this folder will also be encrypted. Generally speaking, this is the option most people will choose.

When you select "apply changes to this folder" only new content in the folder will be encrypted. Existing files and folders will not be encrypted. Generally speaking, this would not be an option people would use, but there are some cases where it is useful.

FYI: This also applies to Windows built in folder compression. The options make more sense when it comes to compressing folders contents; compress everything or just compress new items.