'indexes' has been a just-fine variant of the plural for a very long time -- actually it's the first one listed in Merriam-Webster, so probably the more common variant, though I haven't dug into other references. That said, you're correct that the more common or preferred variant will depend somewhat on the culture/community/industry. The house style guides in finance probably tend toward 'indexes' -- in part because an index is a branded product they produce, so consistency is important -- while software/tech companies (or at least people in them) may tend prefer 'indices'.

Why do they need a justification? English is under no obligation to imitate Latin plurals, and it adds no functional benefit.

Edit: interestingly, the title of the article uses the English, while the body uses the Latin (although in one case that’s because it’s from a name).

Edit2: Relatedly, I had a "shower thought" that even the most pedantic Latinophiles say "albums" instead of "alba". Although I also know a Latinophile who reluctantly used "alba" for a folder on his music app -- but that was only because "albums" was a reserved word.

Looks like a super common question - nasdaq has an article about it: https://www.nasdaq.com/articles/indexes-or-indices-whats-the...

The real puzzler is how they used both spellings in one headline.