You said you needed to think on this some more.
Here is something that I just thought about.

Shouldn't the fluid be at least as warm or warmer as the engine coolant in the radiator. 87 to 92 degrees centigrade.
I always thought.... The torque converter and gear friction heats things up on long drives.
Any excess heated that's generated is suppose go out its heat out through the radiator.

I would think the radiator would speed up getting the oil up an operating temperature.

How long is that commute you take anyways? Maybe there is more condensation than fluid in the bottom.

Maybe the pump is not making enough pressure or there is a restriction of flow amount in the valve body to properly make the shifts.

I just recently bought another Volvo, my first '92 and with an automatic so, I wonder if you can troubleshoot this from an outside port like on the M 46?

Phil