Simply not true. Linguistically, Ukrainian is closer to Polish than to Russian.

Russians perceive Ukrainian as closer to Russian because all Ukrainians in Ukraine speak Russian. I met once a Ukrainian born in Chicago, who spoke only Ukrainian but no Russian. He met a Russian fellow at some conference. They could not even start a conversation when one of them spoke Ukrainian, the other Russian, which upset the Russian guy, because as you claim, he believed that Ukrainian is just a dialect of Russian.

On the other hand, when my Ukrainian friend speaks Ukrainian when calling his family, I can understand what they are talking about. But for a business conversation, I would hire a translator. Or switch to English.