"Redcards cannot be added to Apple Pay as part of this rollout", a Target spokesman confirmed with MacRumors today.
This means paying with a REDcard will still require inserting the physical card into the payment terminal or adding it to the Target's mobile app and having the cashier scan a barcode at the checkout. The latter method requires you to open the target app and tap on the Wallet tab to access the barcode.
Both options are less convenient than Apple Pay which requires a quick double click on the Page button and approval with Face ID on the iPhone X and later or short rest your finger on Touch ID on older iPhones.
Target already suggested that Redcards would not support Apple Pay on Twitter but its "current" formulation was not quite clear.
Of course, Target can decide to allow Redcards to be added to the Apple Wallet app in the future. The dealer had avoided accepting Apple Pay for several years until he turned course with this week's announcement, so it can only be a matter of time before it changes again.