I also can't imagine why it would have been changed.
I went looking. Searching one of the part numbers quoted by Oberon, GU05086330, I got this at Stein-Dinse
https://www.stein-dinse.com/de/moto-guzzi-kupplungszylinder-850-1100-1200-breva-griso/item-2-1030607-GU05086330-.html
Looking at these parts lists, choose "clutch" from the index, part #13 on the apparently same drawing in all of them, I got the part number GU01086330 on all of them.
https://guzzitek.org/parts_list/gb/1100/V11/V11Sport-RossoMandello_1999-2001_062011_PL(GB).pdf
https://guzzitek.org/parts_list/gb/1100/V11/V11LM_Naked_2001-2002_052013_PL(GB).pdf
https://guzzitek.org/parts_list/gb/1100/V11/V11LM_Nak_RC_NC_Cat_2003-2004_062013_PL(GB).pdf
https://guzzitek.org/parts_list/gb/1100/V11/V11LM_2002_062011_PL(GB).pdf
https://guzzitek.org/parts_list/gb/1100/V11/V11Cafe_Ballabio_2003-2005_062013_PL(GB).pdf
So my opinion:
Firstly, it seems that the V11 models did indeed all have the same clutch cylinder.
Secondly, the clutch cylinder pictured from Stein-Dinse is listed as being for the "next generation", i.e. Breva, Norge etc., but looks remarkably similar to the clutch cylinder on my V11.
So, even though the Oberon part is apparently not specifically listed for the V11 models, I reckon I'd be willing to take a punt on it. If only because it comes in such pretty colours.