It’s likely the latter. The fact that post-protocol treatments occur in oncology trials is perfectly normal. It is not ethically right to lock patients into a research protocol. Patients have the right to withdraw and can be offered other treatments. And when the endpoint is far off, such as survival, a lot of water will flow in the Aura River between the treatment and the endpoint.
The fact that this comes as a surprise, leading to a change in strategy, is either A) making excuses that will be bought by 20,000+ retail investors, or B) total incompetence in the design of a Phase 3 study.