Welcome to Flyertalk. There is lots of information scattered around about what happens to your credit score in this hobby. Yes, a high credit score will likely take a hit, but what you do next makes a big difference.

To answer your question directly, yes, anytime after the first day of an AOR, the credit report will show the pulls. Yes, the reason to apply for multiple cards in one day is to get multiple approvals without the new credit being a factor. What you do next is a personal choice.

I've done 1 app o rama, in my life...last fall. My husband also has done one, plus 2 add on cards. I found that is enough points for me overall, for now, and enough to keep track of. I have added 1 AA card since then, and will pounce on the next good offer that tickles my fancy. Adding a card or two a couple of times a year is plenty for us, and, unless my points "spend" changes, I think I'll just keep chugging along.