This right here is why Ichigo should never have been allowed back in the human world.
Regular captains and lieutenants need a reiatsu limiting gentei kaijou seal on them to be allowed to go there at all.
Ichigo, base-line before he reaches this version of Aizen, had the reiatsu strength of three captains.
Ichigo overwhelmed this version of Aizen, then went on and overwhelmed and defeated a several times stronger version of Aizen.
And then he finds out more than half of his reiatsu was sealed all along and his reiatsu is so strong when he's going into battle it nearly causes a physical manifestation.
Even with a gentei kaijou Ichigo shouldn't be able to be in the living world because that seal works on a percentage and limits reiatsu to 1/3 - which would put Ichigo at the level of a captain before the seal.
Ichigo, by the laws of how everything works and his own skill level, should not be able to walk down the street in Karakura without leaving a line of broken bodies like Aizen did.
Aizen was not TRYING to kill those people. He even warned that guy to not come close. Aizen is extremely skillful in precise things and can absolutely restrain and control his reiatsu to a degree Ichigo is not able, and may never be able, to achieve, and he's STILL accidentally killing humans that get within a certain radius of him.
He's still blasting semi-to actually powerful shinigami's limbs to reishi dust when they get close to him even with Kurotsuchi's specially made seals and bindings and chair designed to keep Aizen's reiatsu close to his body.
Aizen never touches ANYONE but Ichigo and Yhwach after he fully transcends himself with the hogyoku.
It's entirely possible he CAN'T. That this is not an aspect of himself he can turn off and he's just permanently separated himself from everyone else in a every sense of the world.
That no one can even come close to touching him. That they won't even get to the point of being in physical contact with him before their hands cease to exist.
But Ichigo can lay his hands on his bare skin.
Ichigo may be "weak" enough his reiatsu isn't insta-killing shinigami and souls able to withstand reiatsu, but he is definitely not weak or skilled in reiatsu control enough he should be able to be in the world of the living around souls with zero immunity to reiatsu.
Also: what a heady thing that must be for Aizen after all that isolation, to know there's one single person out there that can touch him.
And how obsessive and quietly needy that might make him. There's only one person who could ever touch him again for as long as he exists.