They are obviously referring to all the political discussions. This would have to include all the debates in Parliament over the Safety of Rwanda Bill which didn't end until April 2024. Otherwise it would be a meaningless and arbitrary statement. And Oxford University don't do meaningless and arbitrary statements.
This is how they constructed that paragraph:
The initial premise:
They give one example:
They conclude:
It means that all the political discussions and debates had no deterrent effect. And as we know, those discussions and debates didn't end until the Spring of 2024.
And they then move onto say that we will never know whether it would have had any deterrent effect if it had gone ahead because it was cancelled.