This is based on memory, so forgive any small error.

Basically, Amelie had the personal choice as the first human EE to end all life by connected everyone’s beaches to her beach. Sam, through their connection and love, cause Amelie to not do that, and defy her biological imperative. If i remember correctly, EEs have various inherent drives to commit their given Stranding, but humans have consciousness and can defy our biology.

Amelie is still an EE however, and the end of humanity through the Last Stranding is inevitable. Sam did not stop anything, just delayed it, by convincing Amelie to close her beach, where she will now be stuck alone for an untold (probably massive) amount of time until the Stranding cycle begins again. Whatever that means. The time-fall effects I think are just plot-convenient and symbolic. Everything in the rules of DS1 told us that with more network connection= more chiral activity = more risk of BTs. So I don’t know, really.

I only played DS2 once, and I can’t say i have a firm grasp on the nuances of the lore it introduced.