Performant mesh manipulation code as a rule deals with largish float arrays (or other similar contiguous layouts, like AoS or SoA or indexed versions thereof). So there are no per-vertex objects to malloc/free or to track in GC.

In some algorithms, other data structures such as trees, may be used used as intermediate formats, but there too the options to use malloc/gc allocated nodes vs alternatives is similar in a GC'd vs a non-GC'd language.

In general, good GC's often outperform malloc/free. Because GC's are amenable to parallelization in the background, and because malloc/free don't enjoy the bump-allocator style happy case that is used in generational GC's nursery objects.