You should find some submissions done by myself.
HPC# job is only to replace those parts currently written in C++, everything else is written in plain C#, with GC, as Unity always was. In fact they have migrated to .NET 4.6 with 4.7 on the roadmap.
Just like Unreal uses C++ with GC, but naturally in performance critical paths they resort to other techniques.
Which isn't much different than on the old days, avoid malloc() and new on the performance critical paths.
Just because there is a GC available doesn't mean one has to use it for every single allocation.
Unity's ECS is implemented in a OOP language, C#, and anyone that has spent some time in the CS literature about component systems, knows that they are just another variation how to do OOP.
One of the best sources uses Component Pascal, Java and C++ (COM) to described them (1997), with the 2nd edition (2002) updated to include C# as well.
"Component Software: Beyond Object-Oriented Programming"
https://www.amazon.com/Component-Software-Object-Oriented-Pr...