Class E or Class G - another one of those that makes you go 'hmmmmm'

We all know (or should) that when a Class D airport tower closes, the
airspace reverts to Class E or Class G and is specified in the A/FD.
Question is what determines which airspace it reverts to???

CFI Test Prep question 6930 answer states, "When that tower ceases to
operate, it reverts to Class E Airspace. Without weather reporting
capability, Class E airspace reverts to Class G airspace. (AIM 3-2-5)".

AIM 3 - 2 - 5 states "At those airports where the control tower does not
operate
24 hours a day, the operating hours of the tower will be listed on the
appropriate charts and in the A/FD. During the hours the tower is not in
operation, the Class E surface area rules or a combination of Class E rules
to 700 feet above ground level and Class G rules to the surface will become
applicable. Check the A/FD for specifics."

The AIM doesn't help here but the test prep implies that without weather
reported capability, the airport reverts to the less restrictive Class G.
So, we look at our favorite sectional (in this case, Seattle), and we see
that, in most cases, part-time towered Class D airports under the Class B
veil go to Class G while those outside go to Class E (weather reporting
capability doesn't seem to be a factor). Then when you look at Pasco (KPSC),
we see it is not under the Class B airspace but reverts to Class G AND has
weather reporting (ATIS and ASOS).

So, can anyone enlighten me as to the rule behind this? Does it have to do
with sunspots and the phase of the moon?