Once again, we see the branches literally be erased once the stones are returned, so I believe your interpretation is flawed. I'll concede that things are sticky with the Space Stone and Power Stone, but from what I understand, the split timeline where Thanos, Gamora, and Nebula go to the future is essentially cut off once the stone is returned. Those events happened and then they didn't. The space stone is a bit stickier, but we also dont know specifically what happened when Cap returned the stones. The fact of the matter is that if it were all alternate timelines, then cap aging would set him to be in an alternate timeline and not back in the original one.
Completely agree, she shows that once you go back and replace the stones, branched timelines no longer exist. Of course the plot hole is that not only would he have to replace the stones, he would have to stop all interactions made. Replacing the sceptre doesn't stop Cap from fighting Cap for example.
If old man cap was from an alternate timeline he couldn't return to theirs, the device Stark made navigates them back to their quantum machine in a set time and place. He couldn't make another and jump to a different timeline, that makes no sense.
So he had to have gone back and been with Peggy in the same timeline. Just assume she kept it a secret which I imagine she was good at and when she says 'Steve, you came back' during the Winter Soldier, it may have been she believed he came back in time yet again as a younger Cap. She also had dementia.
He clearly ages as well as Rocket who would be a very old raccoon.
If old man cap was from an alternate timeline he couldn't return to theirs, the device Stark made navigates them back to their quantum machine in a set time and place. He couldn't make another and jump to a different timeline, that makes no sense.
So he had to have gone back and been with Peggy in the same timeline. Just assume she kept it a secret which I imagine she was good at and when she says 'Steve, you came back' during the Winter Soldier, it may have been she believed he came back in time yet again as a younger Cap. She also had dementia.
He clearly ages as well as Rocket who would be a very old raccoon.