Good suggestion.. but looking at your reputation, i am guessing you are an experienced steemian who understands how platform works.
But most people dont..
The only reason i included owner key in this diagram is because the "Permissions" section still shows Owner key as one of the keys. However steemit also uses the term Master Password as well.
Hence i decided to include all to avoid confusion amongst newbies who would go to their Permissions settings and then they will start wondering what Owner key is since it is listed seperately over there..

A long time ago. Owner key was not the public key of Master Password.. it was altogether a different key that could perform all functions except "memo key" functions.
However, in latest updates, the function of owner key has been revoked yet it still shows up in the Permissions section. I am guessing that future upgrades will have something to do with this. Otherwise, they would have totally omitted the term Owner Key..