LiveScience.org mentions the same question back in 2020
Of note, it’s unclear whether the dog died a natural death, or whether it was killed to be buried with its human. An analysis of its remains may reveal this mystery.
I couldn’t find an answer though. Most online sources of the discovery are from back in 2020, then it’s just memes.
I feel like it also depends on where you go. It’s a big country and the culture can be drastically different in different areas, even within the same state.