check out the talk pages. each ship was confirmed to have been sunk by some authorities and had a highly detailed account of the event published by some media
It seems like mostly fog of war combined with media's incentives to have great stories. Really the Ukrainian military is not going to connect it's PR department up to its tactical to get a real soldier to confirm which class of boat was hit. It also serves them quite well that Russia might not understand which threat cost them the Moskva.
that is very likely the case, because the Ukrainians have lied before and afterwards about similar ships
https://en.wikipedia.org/wiki/Russian_patrol_boat_Vasily_Byk...
https://en.wikipedia.org/wiki/Russian_frigate_Admiral_Makaro...
check out the talk pages. each ship was confirmed to have been sunk by some authorities and had a highly detailed account of the event published by some media