Skimmer line connected to main drain

Hello,

I closed my pool last week and remember the company that closed it tell me my skimmer line was connected to my main so they can completely blow out my skimmer line because water from the main drain is pumping water into my skimmer line. He said I would have to drain all the water from my pool to blow all the water out of my skimmer. So he did his best and added antifreeze to the skimmer to the top. Just wanted to see if anyone here had a similar issue with their pool? I live in northern VA so I don’t think it will ger extremely cold. Should I be worried?

Thanks!