Fast Compression backup filenames not incorporating LiteSpeed variables specified in Backup Wizard (4246356)

In the Backup Wizard, we configured LiteSpeed variables such as %DATETIME% in the 'Backup Name' field of the 'Select Backup Type' UI screen. These variables are included in the generated backup names when, on that same UI screen, the 'Backup Type' radio button is set to "Regular backup".

When we switch it to "Fast Compression" though, the LiteSpeed variables are ignored; they don't show up in the name. The names generated have no relation to what we have configured with variable names. We get names such as: