There is an obvious bug in the for AbstractMemorySegment::reinterpret(long, Arena, Consumer):

@Override
@CallerSensitive
public final MemorySegment reinterpret(long newSize, Arena arena, Consumer<MemorySegment> cleanup) {
    Objects.requireNonNull(arena);
    return reinterpretInternal(Reflection.getCallerClass(), newSize,
            MemorySessionImpl.toMemorySession(arena), null); // <------------ note the null here
}

The cleanup is not passed to the "internal" function. As a result, no cleanup function will be called when the segment is closed.