No one reported a firm agreement on that structure like they are with the €75m + €10m now. Ducker himself literally included the phrase "broad agreement" in his article. Ornstein himself was reporting whatever Romano was (i.e. €65m + €20m) and even stated that the structure & payments needed to be negotiated despite an agreement on the total value. Romano himself didn't even state that there was a full agreement on that structure as they were still discussing the add-ons. If the €20m couldn't be agreed on, then that changes the whole deal, which is what we saw happen here.
When I look at this from your perspective, here's what could have happened: we agreed on the total value with Barcelona, and Barcelona were also okay with the base fee despite not fully agreeing to it. That base fee was contingent on how the add-ons would be paid out and structured. Barcelona probably didn't like how the €20m was getting structured; maybe they wanted more of that to be easily met; maybe they wanted more of that amount up front sooner depending on the objectives. Whatever the case, United decided to add €10m to the overall structure, but that extra amount may be deferred to future years instead of being paid up front. We don't know the exact structure, unfortunately.
In short, if we did have a full agreement on the whole fee and structure, then we would never have seen today's report come out.