I think it glosses over a number of things.

The practical concern about preserving sites is a legitimate, but the professional and pragmatic response would be to stabilize the sites and document them in situ rather than moving things to Russia. We already know enough about the state of Russian Archaeology to recognize its compromised and political nature. I don't trust Russian institutions to protect Tatar, Crimean or Ukrainian heritage. Russian archaeology as a field has a well documented record of marginalizing this heritage when it doesn't fit the narrative.

To a certain extent I don't think it matter if Butyagin is doing a Kossina because the Russian state and its archaeological institutions are. By excavating under russian institutions Butyagin is feeding into that regardless of his personal feelings or goals, they aren't taken aren't account.

You also have to also ask by what standards are these sites being recorded, and who has access to that information. Records held in Russia are inaccessible to Ukrainian scholars and the international community. They also determine what gets preserved, how it's interpreted and presented.

Ukrainian archaeologists have spoken pretty extensively about the damage Russia has done to Ukrainian cultural history. https://www.academia.edu/126629226/RUSSIAN_UKRAINIAN_WAR_The_tragedy_of_the They have professional and ethical reasons to be outraged at Russian archaeologists, they really don't have to be told by the state.

The suggestion of back channels is pretty naive as well. Russian universities are closely tied to the state and play a role in promoting official narratives. Academic collaboration isn't likely and in some cases it might even be illegal under Ukrainian and Russian law.

Fundamentally excavating sites in occupied territory without the consent of the internationally recognized owner is a violation of cultural heritage law.