Thanks for the clarification - I thought it might be the usual exclusion of central and eastern european nations, despite data being collected by google.
I know, I was being sarcastic. This article should be flagged as it has no scientific meaning in the context of ... “European countries” as it ignores quite a chunk of data.
Google publish data for everywhere. (At least, I see Bulgaria, Croatia, Czechia... )
https://www.google.com/covid19/mobility/