ok true, that you walk out with 2 degrees in both situations. However in the second scenario, there are different rules(I think) I spoke to someone about it. Apparently in the "Combined degree" you can mix up subjects from both degrees, however in the "Double degree" you cannot. Does this happen in other unis or something?
I may be wrong, but the point is, is that you can't enrol in Science/Engineering "double degree" as something different to Science/Engineering "combined". The usyd website only shows one degree (ie. Science/Engineering combined). The latter is a still a double degree.
This is just me surmising, because I do neither science nor engineering nor have talked to the respective faculties but I would think that the different rules will be because you are transferring into the combined degree at a later stage, and thus would probably need to complete subjects that combined students have already completed (or they may even reduce the subjects you need for some reason). The reason you can mix up subjects in Engineering/Science is that you will be doing components of both degrees alongside each other (eg. something like 3 subjects of Engineering and 1 of Science a semester), whereas if you start out doing just Engineering, you can clearly only do engineering subjects until you transfer to doing Engineering/Science- so from your first post, if you start out doing just Engineering for 3 years then decide to transfer to Engineering/Science you will probably have to do a heap more Science subjects in 4th/5th year because you need to catch up for what you missed when you were only doing Engineering in your first 3 years.
I hope that makes sense.
I think the same thing works for Science/Arts- basically you can if you want start out just doing a Science degree. You can then in 3rd year for example, decide you want to also do an arts degree- they will let you then (to be honest i'm not sure though whether this is essentially transferring to arts/science or whether it is enrolling in an arts degree and getting credit for prior studies) do arts subjects for a year and somehow come out with an Arts degree. Personally I think its devalues an Arts degree to allow you to do arts subjects for a year and then suddenly have an arts degree when everyone else spent 3 years getting one, but that's my own personal view, and in the end, the university can do what it likes.
Edit: It may in the end, be just like the Arts/Science example - eg. USYD will now let you, after having done an Engineering Degree, tack an extra year onto your degree, do all science subjects, and come out with both Engineering and Science degrees. The requirements of getting both are:
"To qualify for the award of a combined Engineering/Science degree a student shall complete units of study to a total value of at least 240 credit points including:
* 96 credit points from science subject areas
* units of study as prescribed in the BE Specialisation Requirement tables for the specialisation that the student is pursuing, and
* a major in a science area."
96 credit points of Science is essentially 16 subjects, so a year and a half worth of science study....