Of course, meeting your offer puts you in the strongest position.
But you need to get an offer to start with. If you apply with lower grades in hand, and they make you uncompetitive or are even below the standard offer, you won’t get an offer in all likelihood.
I agree (as I said in my final point) that flexibility is more likely to be shown if NOT deferring. A lot depends on how competitive the course is. Most courses are recruiting not selecting courses. Unless a selecting course, if an offer has been made and missed by one grade, many places will confirm even a deferring candidate.
The point I. Was making, is that candidates applying with grades in hand, often have less opportunities if where to apply to or where will give offers, than if they’d applied with their (usually higher) predicted grades, whilst still in 6th Form. It is often weaker candidates who decide to wait and see how they do. They often haven’t worked out what they want to do or been to Open Days etc and decide to wait until they have grades. Yes, that buys them time and means they don’t have to think about uni applications whilst studying - some decide it’s best to just do one thing at a time. But when they achieve their results below their predicted grades (and this is what happens in the vast majority of cases) they close off a number of courses they can then apply to post-grades.
Yes, you can never guarantee any uni will take you if you miss your offer, that’s true. But you are more likely to get an offer with higher predicted grades than lower actual grades. And getting an offer is an absolutely vital part of the process. If you firm an aspirational place which you may well not get the grades for, it’s even more important to have a realistic insurance place.
By applying post grades, you might only be able to put the insurance place as your top choice, as the other place won’t consider you. By applying with the higher predicted grades, you at least have that chance to get an offer. You’re not really worse off if you don’t make it, especially if deferring as accommodation will be allocated following year, and by then you’ll be an unconditional anyway. If you are fully aware that flexibility might not be shown, taking the chance of applying apsirationally, esp if not deferring, is a risk worth taking for lots of people, as they will find themselves on a course with grades slightly lower than the advertised standard offer. In fact, more course than people think will have a good number of people on the course with lower than the advertised standard offer. They need to accept those people on results day in order to fill. And they’d rather take them than risk Clearing which could deliver weaker candidates or nothing.