Yup, most of Eastern Europe are Balto-Slavic. While the division from the Eastern Slavic languages (Russian, Belarussian, Ukranian, etc) is distant, they are still Slavic. From Eastern Europe, only Estonian is not a Slavic language.
I regret being that loose with the designation :), Romanian and Hungarian are valid counter arguments.
In my mind, I was thinking of the belt of countries between Russia and Central Europe, starting from the Baltics down to the Balkan (excluding Greece).
Even by your definition, I can count at least seven countries where the official language is not Slavic. And that's not even including all the Altaic, Romance and other assortment of regional languages, many of which have some sort of official status.
Some of my fellow Romanians will also claim they're Central European, but in my mind, all the ones I listed are Eastern European countries. I'd even include Turkey and Kazakhstan in there, part of the latter is to the West of the Urals, which is what we normally consider the border between Europe and Asia.
That's cute. It is clear thats an outdated political organization and not geographical. Read at the groupings. Greece is more eastern than Albania (and it is one hour off timezone), and it says 'western' which is not the case by any geographic means.
“There’s a question” implies that there is a ground truth that might be discovered to resolve this rather than simply a clash of different purely arbitrary definitions of the same terms.
The Visegrad 4 (Poland, Czechia, Slovakia, Hungary)are generally taken to be "Central European". The strict East/West division is largely a product of the Cold War and the Iron Curtain.
No, the distinction into West/Central/East Europe was also relevant in the centuries prior. You're right with, that East Europe starts with Belarus, Russia and Ukraine.
Ah, yes, how could I forget! As a side note, though also Finno-Ugric then similarity in sound and appearance from Finnish or Estonian at least appears very far.