Long answer: if you're the DM, know that Lucky is a seriously poorly worded feat. It can be read differently in more than one place, yielding terribly broken results. My suggestion is that you adjudicate it in whatever way you want, and if a player objects to it, do not attempt to discuss it and just ban the feat.
Edit: by the way, if you want to try and understand the RAI - "rules as intended" for the Lucky feat, do not read the "Sage Advice" about it (which typically answers in terms of RAW - "rules as written") but instead double-check what is said under "Advantage and disadvantage" on PHB page 173.