Yeah, I didn’t buy these items - but it would seem that they would not provide extra bonuses but rather allow alternative set builds (which may allow extra bonuses I guess)
I would have liked the idea of extra gear pieces for each set to allow for some flexibility in building set bonuses (not extra bonuses, but different combinations to get the existing Set I II & III bonuses)
Based on the naming, the descriptions and the MONTHS long timeframe for any sort of indication about which way this was going to end, I can understand if those who paid money for these items feel this decision is not a fair one (in addition to the explanation of the decision not making much sense)