Transmission fluid level

I would have to say, no you have it correct.
This is what the repair manual says, I do not know though if it is the same as what your owners manual says or not, since I don't have an owners manual.
Automatic Transmission Fluid > inspection.

NOTE: The level of ATF varies with fluid temperature. Pay attention to the fluid temperature when checking ATF level.
1. Raise the ATF temperature by driving a distance of 5 to 10 km (3 to 6 miles). Idle the engine to raise ATF temperature to 70 - 80°C (158 - 176°F) on Subaru Select Monitor.
2. Make sure the vehicle is level.
3. After selecting all positions (P, R, N, D, 3, 2, 1), set the select lever in "P" range. Measure the ATF level with the engine idling for one or two minutes.

Fig 1: Identifying ATF Level Indications
G03807317
Courtesy of SUBARU OF AMERICA, INC.

4. Make sure that ATF level is above the center of upper and lower marks at HOT side.
NOTE: When the transmission is hot, the level should be above the center of upper and lower marks, and when it is cold, the level should be found below the center of these two marks.

5. If the ATF level is below the center between upper and lower marks, add the recommended ATF until the ATF level is found above the center between upper and lower marks.
CAUTION: 1. Use care not to exceed the upper limit level.
2. Remember that the addition of ATF to the upper limit mark when the transmission is cold will result in overfilling of ATF, causing a transmission failure.

6. Check ATF level after raising ATF temperature to 70 - 80°C (158 - 176°F) by running the vehicle or by idling the engine again.
7. Check the ATF for leaks.
Check for leaks in the transmission. If there are leaks, it is necessary to repair or replace gasket, oil seals, plugs or other parts.

How cold? Just an hour or so or overnight?

As long as it is not overfull once it gets warm/hot I think you are okay. The transmission does not stay cold very long, it warms up about as quickly as the engine when driving.

I agree with you though, it does seem odd, almost like the fluid is not expanding when it gets hot.
Maybe it is due for a complete fluid change.

You are welcome!