No my explorer caps at 2.8 on a 25gbe connection.you said yourself that altho you have SMB direct, your explorer caps out at 2gb/s ???
Small files will run 2.8GB/s without problem.
Files over 50GB the speed will slow down some but in general I can maintain over 2.4GB/s until my basic m.2 drives either run out of cache or start to warm up.