My first thought was regarding two groups
- those freshers who don't live in halls (for reasons of personal preference / caring responsibilities meaning that they have to commute / not actually qualifying for university accommodation because their home address is too close etc)
- everyone not in first year and therefore unlikely to be in university accommodation (second year accommodation groups coming together through many routes, not just meeting people on one's own course).
Out on the real world, so to speak, shops don't insist that all those shopping at the same time are only from a group living together and so on. Even where all students live in halls, what happens where all but one person taking a particular module have applied for and can afford an expensive hall of residence and the last cannot afford to live with them? Does that person get allocated the same accommodation but e.g. with the difference made up with a bursary? What about the many more hours in the week when the students are not attending teaching sessions - will the universities insist on restrictions on the students' personal freedom in excess of the current government rules?
I'm not saying that I can't see why the 'bubble' idea might have been put forward, just that at first glance, there seem to be quite a few practical problems attached.
The decision as to whether to ask to defer is yours, of course, but the decision as to whether you will be allowed to rests with the university.