There is no evidence of Accelerator adding properties or vectors to the laser to do anything special to Mathers, in fact the narration says that Accelerator just sent it back with double the power, so you would need evidence for Academy City's orbital lasers being at the kind of levels you want for the laser beam to not count as a point against him being High 6-A.
The optical attack had already been launched straight down from satellite orbit. And where was Academy City's #1, Accelerator, who Mathers himself had intercepted with a stomp earlier?
"Reflection and focusing. It is high time you experienced just what Academy City can do, you philistine."
An even greater attack shot back up from below as if to rebel against heaven. The #1 had taken the satellite weapon head-on and then sent it right back with double the power.
If you're talking about him destroying the Sisters DM replicas he was using Mugino's meltdowner beam. The "new form and properties" bit is about how he turned a single beam into a wider attack to take three of them out completely instead of the thinner beam harmlessly piercing through their bodies. If he could do that with any attack he would have taken out Kakine's regular DM clones earlier instead of running away.
I'm not saying that defeating Saints is a debunk, I'm saying that Aleister's best physical feat pre-Bible is defeating Saints, and yes, SchroKatze is arguing that both of them being physically High 6-A would not be an outlie rso you would need more evidence of blood sacrifice + bible being such as huge upgrade as claimed by SchroKatze.
Characters being moved or not by attacks in fiction is usually decided by dramatic tension. Accelerator merely punching him sent him away through several gravestones, yet the LPR and Aleister's attacks during their duel fail to do launch him despite both being stronger. So no, him being in the same spot when Touma can look at him again is not good evidence for him tanking it. I can argue that the LPR just tore a hole through his body that he regenerated while Touma couldn't see him and my argument has the exact same value as yours because neither of us have any actual evidence to support it.
You're wrong, Accelerator immediately points out the possibility that the thing that messed up his attack was Mathers having a different body structure, and Aleister confirms it when they find out he and the others are grimoires. It isn't a defense feat, and if Accelerator was using his full power he would have used the earth's rotation and/or caused more collateral damage than that.
"What the hell is going on?"
Those words were far removed from scientific or logical.
He sounded like he had run across a strange jinx.
"I tried using my reflection to shred all his blood vessels and nerves. So did I screw it up, or does the human anatomy in my head not apply to him?"
[...]
And on that note, why had Academy City's #1's special attack ― the one that destroyed all the blood vessels and nerves in the target's body ― failed to work on him?
The answer was simple. An original grimoire would never want to come in contact with Imagine Breaker. And since he was technically not human, it was no surprise his circulation of blood and bioelectricity differed from a normal person. So even if Accelerator was the best the science side had to offer, it was only natural his calculations had not fit.