Question:
Why is the imperfection always displayed graphically with a displacement at the column base?
Answer:
In the graphic, imperfections are always oriented on a support. In the attached model and in Image 01, the only support of the imperfection is defined at the column head. Therefore, the imperfection is oriented at this point.
Since the graphical imperfection is in fact an equivalent load, the display is only of visual relevance in this case. The display is not important for the calculation.
In order to orient the imperfection graphically to the upper column head, you could use a rigid member, for example, and arrange the support there (Image 02).
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