Hi ClivePhoto, and welcome to the forum.
I have looked on the internet for this food and, just like you did, I used the review generator using the ingredient list provided on www.gjwtitmuss.co.uk
I think the reason for the low score is that most of the meat comes from fresh source: while this may sound very "natural", actually fresh meat contains mostly water (about 70%) so the nutritional contribution is not very high. This is confirmed by the fact that the manufacturer had to add pea protein and potato protein to raise the amount of proteins, which still gets to a below-average value of 27%.
Also, it seems to me that the food is quite poor in fat (which is not a good thing for dog food) and high in carbohydrates (called NFE on the manufacturer's website). While the former may be partially explained by the "senior" formulation, 9% of fat is a very low figure; I really can't find a reasonable explanation for having high levels of carbs in a senior dog food, given the risks of diabetes.
The algorithm to calculate the food score should however be taken only as a guideline and not as Gospel: much will depend on the individual dog's needs and for obvious reasons the algorithm can't take that into account. I invite you however to look at the feeding guidelines too for every food: while premium foods are certainly more expensive, you will need to feed smaller amounts to your dog (to make an example, a 10kg pack of Orijen lasts much longer than a 10kg pack of Bakers) which will reduce the price gap. The "cost per day" box in every food reviewed on this website will give you a fairer comparison.
A final note on rice: in general, there is nothing wrong with it (particularly brown rice) and it's actually a pretty good nutrient which is also cheap. The biggest problem with rice is that, being a very common ingredient for pet food, it's recently become highlighted as source for food intolerance together with chicken (incidentally another very popular ingredient for dog food).
I hope this answers all your questions.