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No, it's not the accelerations at the start and finish of the journey that's responsible, but the acceleration in the middle corresponding to the travelling twin's turnaround. An interesting approach to the twin paradox is to consider not time dilation but Doppler shifts. While each twin is seen to be moving farther from the other, they appear redshifted, but while each twin is seen to be moving closer to the other, they appear blueshifted. However, the two twins do not see each other symmetrically. For the stay-at-home twin observing the travelling twin, the change from redshift to blueshift occurs after the light from the travelling twin's turnaround has reached the stay-at-home twin. But for the travelling twin observing the stay-at-home twin, the change from redshift to blueshift occurs immediately at the travelling twin's turnaround. Thus, the travelling twin sees the redshift and blueshift of the stay-at-home twin for equal times, whereas the stay-at-home twin sees the redshift of the travelling twin for a longer time than the blueshift.

LQG (loop quantum gravity) predicts the minutest dependence of the speed of light on frequency, which would be best detectable on large populations of high-energy photons with very long astrophysical paths. A good candidate to test this would be a very far away (=> very early) gamma ray burst. GRB 221009A stepped forward some years ago. From: Stringent Tests of Lorentz Invariance Violation from LHAASO Observations of GRB 221009A Although this doesn't totally do away with LQG, it seems to rule out a vast landscape of the LQG parameter space. The somewhat less hyped version of these news is that we are a tad surer that LIV does not occur in Nature.

This does not make sense. Your rocket is analogous to the muons. The clock in the rocket will only show time dilation to observers on the ground, not to those aboard the rocket. Observers on the rocket will see clocks ticking at the normal rate. So it makes no sense to say time aboard the rocket is "really" dilated. There is no greater "reality" for observers on the ground than for observers aboard the rocket. (Observers on the rocket will however see a shortening of the distance it has to travel, relative to objects at rest with respect to the Earth, just as with the muons.) I think you need to abandon this idea of one perspective being more "real" than another. It seems to me to be a fatal error to think in this way.

there is no absolute frame of reference that in itself is not supported by mainstream physics hence one of the reasons why this is in speculation and not mainstream physics. An absolute frame doesn't even exist in any quantum treatment with regards to decays and aging. Those formulas you claimed do not matter in fact show the above quotation as false.

No, in fact I’ve never seen this assertion. In many formulations of the problem these are not even presented; the rocket is already in motion and the clocks are zeroed when they are close to each other, and compared when close on the return trip. It’s the acceleration at the turnaround that matters.

While I’m sorry to see LQG further minimized as an idea, I appreciate the threads reference to what is IMO the best Beatles album 🎶 (homonym jokes work better verbally than in text 😂)

Observed on my recent trip to Scotland:

No it is the lack of any understanding of Einstein's work and life that does the damage, to my mind. It's full of of nonsense such as "exciting" matter to the speed of light (impossible and irrelevant), the notion that E=mc² is some sort of key to making an atom bomb (which it isn't) and so on. Einstein never worked on nuclear fission and his contributions to physics didn't enable anyone to build one. He had nothing to do with Germany's failure to produce an atom bomb. You may possibly be confusing him with Heisenberg, who did work on the German bomb project. Einstein's sole intervention regarding the atom bomb was to sign the letter to President Roosevelt warning of Germany's capacity to build a bomb. The letter was not drafted by Einstein but by Hungarian physicists: Leo Szilard, in conjunction with Edward Teller and Eugene Wigner. In fact they had to explain to Einstein that it was possible to make a fission bomb, as it had never occurred to him. They then persuaded Einstein to sign the letter, as they rightly believed that would ensure the President would read it, their previous attempts to warn the US government having been ignored. So what your story needs, first of all, is a bit of basic research into what Einstein did and the actual history of it. And, if you don't understand the science, don't make up preposterous stuff about phasing effects and atoms lining up. Steer clear of technical details: they add nothing to the storyline in any case and just make the story look silly.