Why didn't Spock and the others scream and collapse? (Spoiler)

[pookha]

It's a separate timeline. The original still exists; it has not been overwritten.

This claim has been made repeatedly, but without any solid proof given.

In all previous time-travel stories in TREK, changing the past has meant the ONE past of the Trek universe gets altered, and has to be FIXED in order to restore the original.

Why would this case be any different?.

ah because the mirror universe and classic trek co exist.
ever seen tng parallels???

what we have seen before that if a character is at a place like the guardian and a time change happens then they become disconnected from "their" time line and shift into the alternate time line.

Your vessel, your beginning, all that you knew is gone..
is what the guardian said..

so because we have seen all these alternate parallel universe before is why i understad what they were attempting to do.