According to Chris Chibnall in a 2022 Radiotimes interview: the original plan for the special was something larger scale and presumably tied to the previous 13th-Doctor-versus-Daleks stories. However, with the addition of an Easter special Legend of the Sea Devils (2022), the budget they were given did not accommodate these plans and a new version of the story had to be written in a week before production.
The first time Sarah is confronted by the Dalek, it says "I am not Nick". This is obviously an in- joke, since Nicholas Briggs provides the voices for the Daleks.
With an overnight audience of 3.21 million this story was the lowest rated episode since 2005 at time of broadcast.