Google loves XML Sitemaps, it gives their bots an easy way to discover all your content. Even better, it gives webmasters a way to see how many of their URLs in their sitemap file were indexed and which URLs were not. But when it comes to how you should structure your XML sitemap file, that is totally up to you.
John Mueller of Google said so on Twitter. John said, "We don't care how you structure your sitemaps -- they're read automatically, do what works best for you."
Here are the tweets:
We don't care how you structure your sitemaps -- they're read automatically, do what works best for you.
— John ☆.o(≧▽≦)o.☆ (@JohnMu) August 1, 2017
Of course, the larger your site, the more likely you will want to break down your sitemap files by category or section. This way you, as a webmaster, can better debug issues with your site as it related to indexing.
But from Google's perspective, it really doesn't matter how you structure your sitemap files.
Forum discussion at Twitter.
