In other words, split everything so that it is a 3 sized piece of work, for example.

It is probably not practical to get everything to one size, but you might be able to get things to 2 or 3 buckets of sizes by working more on splitting. If you do this and the story size is pretty small, then there are other benefits to the team. For example, by having smaller chunks of work to deliver value, you will probably improve the production of value delivered by the team.

The best Teams break their work to down until they can mostly complete work in one day and still deliver value!

To understand why think of a truck going down a narrow alleyway. If there are cars behind the truck, they are unlikely to be able to get past. But if the load the truck was pulling was put on a number cars a slow car could be overtaken by a faster car which improves delivery. Large stories are the truck in this metaphor.