Could be, after all Ukraine is not a member of EU, and it's known to be a very corrupt country. Most of EU has banned anonymous phone numbers and most social media is already blocking virtual phone numbers.

This means, you could probably order a prepaid sim card from Ukraine, get a legitimate Ukrainian number, cheap and anonymous and then use that to register a twitter account.

If so, then it would make perfect sense to use Ukrainian verified accounts for the bot farms, while the servers are most likely hosted in countries with soft laws against bots and reliable power/internet like Romania, the Netherlands or the Nordics.