@Blossomtoes - it's an interesting one because I think there are more minds at work on this and it would explain some of the letter yesterday.
My take is that Braverman wanted to have her specific amendments to the Illegal Migration Act for political value. The fact they might not have been human rights compliant may not have bothered her (drawing on her actions as AG here on Northern Ireland). But to use those powers would almost have been a slam dunk unlawful matter and the legislation would have had to be corrected pursuant to the powers under the HRA.
But, concluding a treaty between governments, using royal prerogative power, rarely subject to judicial intervention on the basis this power belongs to the Crown, which sets out the required standards in a legally binding treaty, not a MOU or undertaking which do not have to be binding, and then amending the Illegal Migration Act to bring in powers to remove, well, do not be surprised if this does happen.