Insight – Google says that an indexed page is not in the sitemap, even though it is in the sitemap

Google's search panel shows that my site is "indexed but not submitted to the sitemap". However, I have specified the URL in the sitemap. That was so long ago.

I have tested it https://www.example.com/annapurna-base-camp-trekking that's in sitemap but Google does not say it.

Is that why my site is not in the top list?

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