Tomato plants are of two general types - determinate and indeterminate - with some that are in the middle of the two. Determinate types are compact, short plants that don't need any support. Many patio, salad, paste, and small-fruited tomatoes are determinate types. No pruning is done to make them grow that way. The other type - indeterminate - produce plants that remain vegetative and can be many feet tall by the end of the season. They are often pruned to remove the suckers that form between the leaves and the main stem. This is done to increase air circulation through the plant as well as being able to get more plants in a smaller space. Number of fruits produced is less, but fruit size is larger. However, this has nothing to do with maknig the plants shorter. I'm guessing that what the gentleman saw is a determinate type. When he looks for varieites, he should look for that term in the description.
