The .NET/C# Driver calls buildInfo to determine the connected server's semantic version and then uses that information in src/MongoDB.Driver.Core/Core/Misc/Feature.cs to determine whether a feature is supported. The Java Driver used to do this too but switched to maxWireVersion from isMaster/hello to determine feature support in the 4.0 release of the Java driver. We should consider this change for the 3.0 of the .NET/C# driver as C# is now the only driver that calls buildInfo and uses it in this way.