Yes but that's entirely missing the original point that how X and Y are packaged affect the possibilities of negotiation.
If you have two separate bills X and Y and X is a thing that lots of people want and Y is a thing that few people want and you are negotiating to get people to support Y your pledge to support X is not going to do much for you because
1. Lots of people are going to support X, X doesn't need you.
2. People who don't support X will be campaigned against for not supporting X.
3. People who support Y will be campaigned against for supporting Y.
So, if it were possible to put the highly unpopular Y together with the highly popular X in such a way that in order to support X which you want to do and which everyone wants you to do you also have to support Y the chance of Y getting through has increased by a great deal. Sure there will have to be collective voting on the combined XY and the combined XY will be less popular than X by itself, thus people may now actually have to make deals to support XY but not as great a deal as they would have had to make to support Y by itself ( especially as supporting Y by itself was probably dead in the water)
This is what the original comment was complaining about, what my example was meant to highlight and yes, either way will require collective voting and bargaining, but if you can slip Y in with X instead of bargaining on them separately you may be able to achieve your goal of passing Y, otherwise there would be a very real chance that you would not be able to come up with sweet enough deals to do that.