Why is it not permissible for men to pluck the middle of their eyebrows?

1) It is said that it is a sin for men to thin their eyebrows, shorten them or pluck the eyebrows in the middle. What confuses me is that plucking the middle of the eyebrow is being regarded as a sin. As far as I can see, those who say that plucking the middle of two eyebrows is a sin all cite verses and hadiths stating that plucking eyebrows is haram. However, the eyebrow and the middle of the eyebrow are different things. If we cannot describe the teeth between our lips as lips, we cannot describe the middle of the two eyebrows as eyebrows. Is there any evidence showing that plucking the middle of the eyebrow is a sin?
2) Again, as far as I can see, everyone says that if the eyebrow is too long (abnormal), it can be plucked sufficiently. It is obviously very relative. What may seem long to one person may seem short to another. Can you describe it exactly? For example, the middle of my eyebrow is not as thick as my normal eyebrow. However, it connects the two eyebrows together. If plucking the middle of the eyebrow is definitely a sin, can such eyebrows be plucked? It is hard for you to describe but, but be sure that the devil tells people that their eyebrows are too long and that they should pluck them.
3) I saw this on a popular Islamic site on the internet: ‘‘It is forbidden for women to thin their eyebrows, but it is permissible for men to trim their eyebrows. (Hindiyya)’’ Is it true?
Note: All the questions I ask are for men.

Dear Brother / Sister,

If there is a curvature, excess, abnormality, etc. in organs such as eyebrows, moustache, beard, nose and ears that disturbs the owner and causes psychological distress, it is permissible to trim or remove them.

Questions on Islam