Fog of war. Truth the first casualty of war and all that. I don’t trust any source completely. All sides have propaganda machines running full speed.
There is video of Putin attending the service, itvaired in Russian state TV, and Globo-lefty Reuters apparently did not find it fake or they would have cast doubt. They aren’t exactly pro-Russia, you know. So it’s quite likely Putin did attend. Not absolutely certain, but quite likely.