It could be because those recipes used to be learnt from the First Aid trainers and because both my tailor toons were trained up to Legion I don’t know what happened there. There are bandages from Battle for Azeroth and Shadowlands that are taught by the relevant trainers.
Checking my Lock’s bandage recipes I see that the Classic and Outland bandages have indeed been moved to her tailoring section. How odd.
Have you had a look at wow-professions web site, there are excellent profession levelling guides there to help if Dugi doesn’t work for you.