If you compare https://maps.wikimedia.org/#10/49.0887/33.3064 and https://www.openstreetmap.org/#map=10/49.0887/33.3064
you will see that the former lacks the large blue body of water in the upper left; this is the Kremenchuk Reservoir https://www.openstreetmap.org/relation/2289192.

Maybe our copy of the OSM database is out of date or the tiles have not been updated recently? I noticed that the Kremenchuk Reservoir is missing on all zoom levels of the Wikimedia tiles. Other reservoirs (e.g. the Kaniv Reservoir https://www.openstreetmap.org/relation/3173129) display correctly in blue, so I doubt it's an issue with the style we use. On OSM, the Kremenchuk Reservoir and the Kaniv Reservoir relations have last been edited 9 or 10 months ago.