The Supreme Court's decision was based on the possibility of 'refoulment' (return to country of origin). Here
As you say, RWANDA has now stated that Those who are not granted refugee status or humanitarian protection, will instead be granted permanent residence so that they are able to stay and integrate into Rwandan society. All individuals relocated to Rwanda will be treated in the same way regardless of the decision of their asylum claim.25 Apr 2024.
As such, the risk of refoulment has gone, so the UK government can go ahead.