Why is my former employer matching dividends in my 401k?

Here’s a screenshot from the recent transaction history (this December) from the 401k from an employer that I haven’t been employed by for many years. The index fund in question pays out a dividend and I see a 100% "safe harbor match" every single time. Is this actually a 401k match from the employer or some sort of glitch?

Elsewhere on the 401k provider’s website it indicates that my 401k amount is fully vested and I don’t see anything else to suggest that these dividends are otherwise not vested, they’re fully owned by me.