As long as we are talking (de)colonization, the distinction makes all the difference.

The difference in the treatment of a land and its people as equals to the rest of the country's citizens and states is what makes Hawaiians regular Americans and Ceuties regular Spaniards, and what keeps Llanitos from being British _citizens_.

To answer your question: yeah, if Gibraltar was a self-sufficient state within the UK (instead of an -arguably- geo-strategic colony that is a tax haven according to the OECD) you likely wouldn't hear as many complaints about it.

Take for example the cession of Sardinia in the very same Treaty of Utrecht. You ever hear complaints about its sovereignty?