UN Resolution 678 states this:
2. Authorizes Member States co-operating with the Government of Kuwait, unless Iraq on or before 15 January 1991 fully implements, as set forth in paragraph 1 above, the foregoing resolutions, to use all necessary means to uphold and implement resolution 660 (1990) and all subsequent relevant resolutions and to restore international peace and security in the area;

It "AUTHORIZES" necessary means and it adds a TIMELINE.

When GW1 ended, Resolution 687 recognized the cessation of hostilities.

This means that in no way can resolution 678 be used to justify GW2. 687 put an end to 678.

Much later, came 1441.
Nowhere is there a timeline nor an authorization like in 678.

Another resolution was needed to justify (or not) a legal war.

Conclusion: Because starting a war is a very serious matter (THE most serious), because it involves so many countries around the world, with so many different languages, because it's a life and death matter, EVERY WORD counts.
I work for an insurance company and we always have to be careful with what we say to brokers, clients. Contracts can be very complicated and must mean exactly the same in french and flemish. If a broker wants something slightly different from what we accept, we have to watch out.

Raoul