[Rohansi]

The GC that Unity is using is extremely bad by today's standards. C# everywhere else has a significantly better GC.

In this game's case though they possibly didn't do much optimization to reduce GC by pooling, etc. Unity has very good profiling tools to track down allocations built in so they could have easily found significant sources of GC allocations and reduced them. I work on one of the larger Unity games and we always profile and try to pool everything to reduce GC hitches.