Consequences of gutter water collecting in corrugated drain pipe
You will not have a siphoning effect unless the corrugated pipe is completely filled with water and no air is allowed to enter it, which will not happen from a gutter draining into it.
No real consequences of the water sitting there. Most of the water will drain out if the pipe is perfectly level, which will be hard to do. The remaining water will be the amount that is &quot;held in place&quot; by the corrugated part of the piping. There will be some air flow from the gutter through the pipe so the water will probably evaporate.