This is not even an RC, it’s a daily (or weekly? don’t remember) snapshot release (can be seen from the missing rc version in the name). And those are always debug builds, which are bigger than release builds as they contain debug symbols.
My understanding has always been that a ‘release candidate’ is supposed to ‘officially’ be ready for release. The idea is one last chance to catch bugs, and if not are found after a certain amount of time the same build number could theoretically become the final release. If bugs are found they can be fixed and a new release candidate issued. Rinse and repeat.