The balljoint boots do not need to tear for the joint to fail.
They are made of a very pliable rubber that is not as prone to tearing or cracking as typical boots found on other cars.

In order to check for balljoint play, the control arms need to be supporting the weight of the car on jack stands. Otherwise, the force of the spring will take up the play, and mask the problem.

They may indeed be fine. Your struts could be the whole problem. The struts are the upper steering pivot point as you say. They may even have some ice in them, and perform poorly in cold weather. I've seen that before on a different car.

The thing is, at 146k, if they have not already been replaced once, the balljoints are probably at or towards the end of their useful life anyways.

On the other hand, if you are very lucky (and there is no visible balljoint play)- the struts are very easy to replace, and you need them anyways, so you do not have much to lose. Put another way, there is not much in terms of a labor savings advantage in doing the balljoints at the same time you replace the struts.

Best of luck.

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1986 300E 5-Speed 240k mi.