Agree with that notion.
Next to impossible for someone outside the Dealer/Bank network to find on-the-run Bundesbank debt to short. Hell, for decades they wouldn’t let US Hedge Fund desks trade it in fact (Ken Griffin at Citadel made a big stink about it)
The play would have been to buy Eurex Schatz Contracts before and now look for a suitable level to short. Smart money is spreading yield curve.