I went ahead and placed an order for a 1-gallon Tipu's Flame and four bands (Wedding Cake, Wimi, Nahema, and Lavender Lassie).
I obviously missed something or the instructions were in error because I never saw a "popup window" for listing my split-stem plant choice and alternates. The gallon wasn't discounted properly either. So I sent an e-mail to report the failure to discount the gallon and to list the split-stem plant information. While I was at it, I asked for assurance that the Wimi I was ordering was the true Wimi and not the solid-colored dark red rose they sent me four years ago.