To answer your query, I’m copy pasting
@m4b ’s statement in which he has explained the whole thing very comprehensively ⬇️
The key feature of Magnus Burgundy is that you don’t need Burgundy status upfront. You can simply get the regular Magnus card and spend as usual. Then, when it's time to redeem your points, you can acquire Burgundy status and upgrade your card to Magnus Burgundy. This allows you to retroactively enjoy the 5:4 transfer rate on the reward points you earned with your Vanilla Magnus card.