Perhaps because it's a relatively modern procedure and because it's typically used for food preservation, but the technique of freezing is almost never considered to be a cookery technique. Cooking is almost always considered to the be the technique of the addition of heat to a dish.
But where would we be without ice creams, sorbets, granaches and other frozen foods? Doesn't the technique of the preparation of these foods also deserve the term of cookery? After all you combine ingredients to form these dishes it's just that they're not heated, rather they're cooled.
To show what I mean, below I include a recipe for an ice cream and a classic sorbet.
Real Chocolate Ice Cream
120g dark chocolate (at least 70% cocoa solids)
2 eggs, slightly beaten
pinch of salt
1 tsp vanilla extract
Place the chocolate in a bain marie (double boiler) and heat, stirring frequently, until melted. Keeping it on the heat, gradually stir-in the milk, whisking all the while and continue cooking until smooth.
Lightly beat the eggs then beat in the sugar until pale and creamy. Stir the hot chocolate mixture into the eggs, beating constantly then add the cream, salt, vanilla and the additional milk. Set aside to cool then pour the mixture into the bowl of an ice cream machine and churn according to the manufacturer's instructions.
500ml fresh orange juice
juice of 1 lemon
finely-grated zest of 1/2 orange
Add the sugar and water to a saucepan. Heat gently until the sugar dissolves then bring to a boil and immediately take off the heat then set aside to cool. When the syrup solution is cold mix-in the orange and lemon juice and orange zest then pour the mixture into the bowl of an ice cream machine and churn according to the manufacturer's instructions.
Alternatively, if you don't have an ice cream making machine, pour the mixture into a non-metallic freezer-proof dish then cover with a lid and place in the freezer. Freeze until the sorbet is almost firm (but still a little liquid). Cut the sorbet into chunks and place in a blender. Process until smooth then transfer the sorbet back into the dish and freeze again until almost firm.
Once again chop the sorbet into pieces and process until smooth. This gets rid of all the ice crystals and makes the sorbet very smooth, which is what you want. Return to the freezer-proof dish and freeze completely. To serve, allow the sorbet to soften for 5 to 10 minutes at room temperature then spoon into dessert glasses and serve, garnished with a sprig of fresh mint.
I would challenge anyone to deny that the method of producing these dishes can't be classed as 'cookery'.