I would normally keep my old hoses but have not had to change mine yet. None of my (huge) collection of old receipts show a hose change so it appears both mine are original at 130,000 miles. My lower hose is 'breathing' oil a bit but seems OK and is not rubbing anywhere that I can see. Thus, as you suggest maybe the 20V engines don't suffer like the other models?
But I asked samco about doing a top hose for 20v and it's them that said they would prefer to sell upper and lower that fit off the shelf.
They are aware a 16v lower will fit if trimmed so who am I to argue with them if they want to do them and they are not charging me any tooling costs. It'll obviously be good for all the Alfa parts places as well as you can also offer an upper hose from samco or a set for 20v
Anyway fingers crossed someone will happen along with an old lower 20v hose so I can send the upper and lower off (pud be great if you could keep an eye out if changing any lowers at your place).