ok, I mostly agree with what you're saying.
Being forceful (or better, strong willed) is not the same as aggression. Certainly many Se ego types are not aggressive people. And yes, getting away from a situation is also using Si. And of course any type can use Se, to different degrees. So we are on the same page there.
Well, for example, Augusta described Se information as "the degree of mobilization, strength of will, power, and beauty of observed objects and subjects." I don't know of any author who denies that (evaluating and applying) willpower is a part of Se. If they did, it would be a significant departure from classical socionics.You said it's part of the core definition for Se/Si, why? (Where you say: "But this is so closely related to the "definition" that I see* no reason to doubt it")
Here are some things Jung says about Se types (again, he makes little distinction between the psychological function and the type):
Jung's description of the Se type is basically as a bon-vivant pleasure seeker: "his aim is concrete enjoyment". This is closer to Si in socionics, in terms of motivation. He also mentions nothing about willpower.
This topic has been done to death but just in case people are willing to listen... consider the following:
1) Jungian descriptions are somewhat different from socionics.
2) Augusta arrived at the modified descriptions over a period of many years, so these differences are not trivial.
3) Therefore, in cases where Jungian and socionics descriptions differ, the socionic ones should be taken as the socionic definition.
So if you recognize that, what does Jung even add to the discussion of socionics? Sure, you can merely write off all the differences you don't like as "stereotypes" but then you are not making a serious effort to learn socionics in my opinion.