TYPO3 Core

Along the rootline, the value -1 represents the current page.

According to the TSref, fullRootLine is supposed to work with negative values: https://docs.typo3.org/m/typo3/reference-typoscript/main/en-us/Functions/Data.html?highlight=fullrootline#fullrootline

But I get no output for key 20 of the following TypoScript:

page = PAGE
page {
    // Renders title of current page:
    10 = TEXT
    10.data = leveltitle : -1

    // Bug – returns no value:
    20 = TEXT
    20.data = fullRootLine : -1, title

    // Just for completion – positive integers will return a value:
    30 = TEXT
    30.data = fullRootLine : 0, title
}

Tested in TYPO3 v12, v11 and v8 with identical results. Is this a long-lasting bug, or was this never supposed to work?