I always feel that the discussion about Master Sets is all about budget. And that has directly something to do with the printing behaviour of WotC in the past and Nintendo these days. What would be considered a complete Master Set 20 years ago, was already considered incorrect when Expedition was released and it got changed again and again with every new block by Nintendo. With the release of Expedition and the reverse holo cards the size of a Master Set doubled. Nintedo been stretching that even further with having 3-30 Secret Rares per set.
And this brings me back to my first sentence; it’s about budget. Not everybody can gather those Championship Exclusive cards to complete their sets. Limit release, scooped up by people many different type of collectors. The pond is to small for all the fishermen, which end up no Master Set for those sets being completed.
For me it always been like this:
Full SetEvery card released in booster packs in their normal print variation.
Master SetEvery card released in booster packs in every print variation.
Master Set PlusEvery card released in booster packs in their normal print variation with addition of every special print and release (e.g. alternative holo pattern of other sealed product, stamped cards (pre-release and alike)).
Also, error cards are not a variation. That’s like putting tomato sauce into your carbonara and calling it a carbonara variation.
Have fun collecting FRLG master sets with all the different print codes xD