Where alternative methods are used, and a student disagrees with a final result, there are likely to be challenges which may come in the form of a Subject Access Request.
The short answer is yes - if a request is made, then you are required to deal with it in the usual way. The fact that information was used for the purposes of the assessment of a grade or mark does not automatically take it outside of the right of access.
If the request is made before the results are published, there is an exemption in the Data Protection Act which allows you to delay the provision of the information until 40 days after the date of the results (or 5 months after the request - whichever is earlier). Therefore, you are under no obligation to release the information prior to the results being published.
However, once results are published you should deal with the request in the usual way.
It is important to note that if the request is received post-results day, the usual one month deadline applies.
It is important to bear in mind when communicating with colleagues about students that the information you are communicating may end up being shared with that student if a challenge is made. Whilst you are not obliged to give out information relating to the calculation or assessment of a grade until after the grade is published, the usual rules apply once the results are published, which could involve release of emails between staff about individuals.