I don't think Maya was claiming unfair dismissal, which only applies to employees who have had a minimum of two years employment. It may be that Maya wouldn't have met either or both of these criteria.
Her case was that by not renewing her contract CGD were discriminating against her, you don't need to be an employee to claim discrimination and there is no minimum length of service.
There's no dispute between the parties that her contract was not renewed, and as there is no claim of unfait dismissal, discussions about whether or not it was technically a "dismissal" aren't really relevant.
Had the judge found that her beliefs meet the Grainger criteria there would have been a further hearing to decide whether or not she had suffered unlawful discrimination on the ground of her beliefs. As it was the legal process ended because of the judge's decision cut off that further argument.