Personally I actually agree with you, but that is not necessarily the Law. I'm not a lawyer, but studied contract law and reading/commenting on contracts was part of my day job. Contract law is full of nuances and ultimately depends on what the Judge thinks. But in general terms Judges don't like vague terms, particularly when there is a big difference in the power of the parties, such as here, big corporation v ordinary individual where they will tend to side with the weaker party. The fact is here "commuting to work" is not clearly defined, it can and was read buy different parties as "commuting the whole journey to work", or "commuting the whole or part of the journey to work". The fact that other major insurers in their wording were far more specific made the outcome almost inevitable.
BTW I always included commuting in my policy and quite a few times added business use. The extra premium for business use was always £0. Now retired so neither applies 🙂