Transforms css shorthand values into an expanded object with each property explicitly defined. This is niche to css-in-js solutions like https://github.com/cxs-css/cxs, https://github.com/styletron/styletron and maybe in the future for https://github.com/callstack/linaria (if they make an atomic module).
When you are atomizing css properties into individual classes at runtime, you can't guarantee the stylesheet order which leads to specifity issues (for example: paddingTop: '20px' followed by padding: '10px'). In this example padding will have a higher specifity and override padddingTop's value.
If you are doing this transformation at build time, you can sort the properties before you write them to a <style> putting generic properties in the sheet before specific ones, but for runtime based solution, padding and paddingTop are unique cache keys and will generate a new className. If padding is added to the sheet after paddingTop, you will not be able to override the value without the use of !important.