It’s a very fair point, sh. All the preamble says is that clues for the same entry are given in order. It doesn’t follow that there are therefore only those two components to the grid entry for that clue. It may be so, but is not a given. And given the lack of a definition for the grid entry there was no way of being sure.
I think those who solved the puzzle using shortcuts not explicitly justified by the preamble need to be a bit careful. Such entries can only be working hypotheses, not confident answers.
This was the nub of my “unfairness” thought. An indication of whether the grid answer contained one, two or three components would have made the puzzle significantly easier. Too easy for some, manageable for others. Naturally those who solved it will usually see it as fair. Survivorship bias.
My entry point, after cold solving 24 clues, was actually 5d. The grid entry formed by combining just the clues was so improbable it “had” to be correct.
I may have misunderstood the preamble, of course!