Hello Christopher2019, When the system is deployed & it comes to pool creation, you can choose to have the system create optimal pool configuration, or manual pool configuration.  When you have the system choose the configuration it will split the drives as your system is showing. The system takes in account all the drives and there speeds and produces the best configuration to achieve the best performance. Here is a link to more support documents & configurations for your ME$ system. [URL] Please let us know if you have any other questions.
Dell EMC ME4 default disk allocate in pool creation with 2 disk enclosures Pool A 0.0, 0.2, 0.4, 0.6, 0.8, 0.10, 1.0, 1.2, 1.4... and Pool B 0.1, 0.3, 0.5...(ie., even no. disks in pool A, odd no. disks in Pool B). Is it the default disks selection / layout  by the Array? Any performance achieve in this allocation?  Any best practices guide shown of it?
Dell EMC ME4 Series disk allocation in Pool