Preloading refers to preloading the document into memory. This is ideal for large documents which would otherwise require an excessive amount of wait time for the first user to access the document while the document loads into memory. So, no, preloading plays no role in reloading a document. Reload times are determined by CPU power along with the speed at which Server / Publisher can access the files /sources it needs to access to pull in new data plus the computational time required to do the specified calculations in the load script.
