Does the streamline contact the ground? It cannot, right? ("no matter can penetrate a streamline")
You can't think of it quite like that. The flow under the wing is properly regarded as a stream
tube. The 'lower' limit of the tube is a streamline running just above the ground. The upper boundary of the tube is a streamline that meets the wing where the upper and lower flows divide, then runs along the wing undersurface (outside the boundary layer of course) until it gets to the TE after which it becomes the running mate of the closest streamline that went over the top.
Obviously the lower limit doesn't actually contact the ground.
The upper limiting streamline is the one that gets affected by the direction of flow off the upper surface, and it is this flow direction/velocity I suggested would vary with vertical position relative to the TE (in free air at least), but now I think about it I'm not so sure it works like that if the upper surface flow is unaffected by height changes. It may be that the downwash angle off the TE is unchanged but as height is reduced the relative areas of the stream tube at the LE and TE change so that the relative velocities change and that is all there is to it.
Does the streamline also "restrict" the passage of the underwing flow?
In the sense that the downward pointing streamline(s) off the TE and the ground hugging lower streamline form a converging passageway, then yes, the streamline can be regarded as restricting the passage of the underwing flow.
Being mischieveous, it is fairly easy to explain this increase in lift/higher underwing pressure using the dreaded Bernouilli, but at the moment I don't see how to explain it using Newton
There must be a way though.