It's nothing written in stone, but it feels as if the lower-rated (and generally newer) soaps were the ones who got shuffled off into odd slots, or at least suffered at the whims of local stations who would air them whenever they wanted (or just not air them at all). The high ratings grabbers were rarely moved far from the slot that the network wanted them aired.
Yes, considering The City was essentially Melrose in New York, lumping it in such an early timeslot made no sense
I would suggest (with little to back it up) that VCR's had become so commonplace---and an essential tool for the soap fan---that the programmers had started to care less about the time slot and more about actual carriage (airing) of these new entries in order for the soap to survive. Noon became (and still is) the death slot for any network-produced fare, which is why they eventually gave up and ceded the slot to the affiliates. The only hope for anything offered in the noon slot was that the affiliate would time-shift it. All three networks were doing it to some extent. As mentioned,
Guiding Light (on CBS) got pushed around by individual stations as early as the 1990s*, and NBC's
Sunset Beach similarly got moved around in local stations' efforts to maximize ratings (either for SB or for its other shows).
* For several years in the 1990s, my local affiliate aired GL at 4pm rather than the traditional 3pm.
Oprah Winfrey was airing at 4pm on another channel, and GL was moved opposite Oprah to cut into that popular program....and from what I remember, it worked! They moved it back to 3pm only when Oprah was moved to a morning slot.