re: So, first time buying in a Walmart store in a while and it shows up in purchase history

In the terms:

When you buy items in-store, we make it easy to see those items on Walmart.com. You can view previously bought items, start a return, and add protection plans from your Purchase History.

When you use a payment card in-store that’s saved in your Walmart.com account, we’ll automatically add your store purchase to your online purchase history – there’s nothing more for you to do. We’ll also add other store purchases made with saved cards in the last 12 months. We'll email you the first time we add a store purchase to let you know it’s available in your account.

To opt-out:
Select Account.
Select Communications & privacy.
Select Store purchases.
Switch the toggle to Off.
Remember, even if you opt-out of store purchases, your Purchase History will still show purchases made with Walmart Pay and any store receipts you’ve scanned with the Walmart app.