That is true — and was demonstrated by the article as its "fix" was to use jemalloc, but even a custom allocator will usually be less performant than a high-performance GC there, because the GC's allocator has more insight into the requirements and workloads.
It might be possible to give that insight to a custom allocator by using the allocator's custom APIs, but this requires a deeper integration between the program and the allocator.
That is true — and was demonstrated by the article as its "fix" was to use jemalloc, but even a custom allocator will usually be less performant than a high-performance GC there, because the GC's allocator has more insight into the requirements and workloads.
It might be possible to give that insight to a custom allocator by using the allocator's custom APIs, but this requires a deeper integration between the program and the allocator.