Google's John Mueller clarified that using hreflang tags does not ensure that a page will be indexed or ranked. He noted that sometimes not all hreflang variations are indexed, and sites may often have one version chosen as canonical if they are similar. He suggested that in cases of 'same language', Google's systems simplify the URLs, affecting how hreflang operates. Additionally, it was noted that hreflang tags are not considered until the respective page is actually indexed by Google.
Just because you use hreflang tags on your pages, it doesn't mean those pages will be indexed and/or ranked in Google Search. Hreflang doesn't guarantee indexing.
In some cases, not all the hreflang variations are indexed. If they are the same (e.g., fr-fr, fr-be), it's common that one is chosen as canonical.
I suspect this is a 'same language' case where our systems just try to simplify things for sites. Hreflang will often swap out the URL, but reporting will be on the canonical URL.
Google has said that hreflang is not even processed until the page is indexed.
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