See the diagram above. The Solar Day has to be the same when the earth returns back to the same Equinox point in relation to the sun. It's looking at the sun at the same position.
The diagrams you cite here, and at the beginning of the thread, are both approximations, not exactnesses (!).
They're intended to show a high-level, general principle of how things work. They have no data, they are merely illustrative. I'll say that again - they have no low-level data (numbers 'n' stuff).
For actual data, you need to look at astronomical textbooks, papers, journals, etc. and see how astronomers of the past figured this stuff out from first principles and their observations.
I'm sure the data, from year upon year upon year of actual observation, is out there to be found, but you won't find it from skimming webpages and lifting diagrams from those pages intended for student or general public audiences.
It will be in the work done by astronomers of university level or beyond. You may need to do some groundwork to find it. It will most likely be in real books, in libraries, and you may need to expend some effort to find it, including asking librarians to retrieve little-used tomes from dusty, remote archives.
Are you willing to do this?
Or is it truly beyond the scope of the 30 mins per day that you devote to this field? If so, just say so.
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