In German the names for recorders were until the 20th century not consistent (cf. Curt Sachs: Reallexikon der Musikinstrumente, Berlin 1913). At latest from the 70s there is a standard for the recorder names (cf. e.g.: Musik in Geschichte und Gegenwart; dtv-Musikatlas; Sevsay: Handbuch der Instrumentationspraxis: Great Bass is in C3, the Bass is in F3. But there is an exception for Renaissance (and rarely for Baroque) music: Sometimes the “Great Bass” is called „Bass“. This is the cause of many misunderstandings about recorder names. I am not as familiar with the English instrument names, but I guess it’s like in German: cf. A. Stiller: Handbook of Instrumentation, University of California Press, 1985; or: https://en.wikipedia.org/wiki/Recorder_(musical_instrument).
It’s true that the range oft he Great Bass overlaps with the Tenor. But for me is the Great Bass no alternative to the Bass because the difference in sound. Also I never would replace the Cello in a String Quartet with the contrabass.
Maybe interesting: Moeck is the biggest publisher for recorder music: http://www.moeck.com/en/publishing/sheet-music.html
In the catalogue are only a few compositions with Great Bass (abbreviated gB), but much more for Bass (abbreviated B).
Andrew Stiller wrote in his Handbook of Instrumentation about the Bass, that the Bass is usually available. About the Great Bass he wrote “very rare“.
I don’t understand the decision of VSL to take the Great Bass and not the Bass.