I just did a gh code search (__finally lang:c++), a hundred-ish instances shows up in ~12 repos mainly related to MS / .Net:

‎ sleuthkit/scalpel‎

‎‎ microsoft/service-fabric‎

‎ ‎dotnet/runtime‎

‎ ‎microsoft/Detours‎

‎ ‎dotnet/wpf‎

‎ ‎Chuyu-Team/VC-LTL‎

‎ ‎apache/logging-log4net‎

‎ ‎microsoft/Windows-classic-samples‎

‎ ‎microsoft/winfile‎

‎ ‎dotnet/llilc‎

‎‎ microsoft/DirectXShaderCompiler‎

‎ ‎dotnet/diagnostics‎

‎‎ SoftEtherVPN/SoftEtherVPN‎

‎ ‎microsoft/PTVS‎

‎ ‎aybe/Windows-API-Code-Pack-1.1‎

I don't think that it's in any way meaningful, it's literally unused given that it's been there for likely 20+ years.