Our group was 2 in Manfredi's and our experience was pre-covid. We've done 1 post-covid cruise and the SSBP wines by the glass were to our liking so we didn't ask for a bottle of something else to be opened. We cruise again on the 15th and they gave us the SSBP to compensate us for a different issue, so we will see if we run into the lack of good wine situation again.
We usually buy the SSBP. Some days we get our money's worth, other days not, so it might be a breakeven sort of thing for us. The reason we buy it is because we really dislike the idea of nickel and diming at the end of a trip. DH would just pay the bill. I would be the person that said "Well, wait a minute. I'm not sure I had a mojito after that excursion". It just saves us a hassle.