Multi tenancy is indeed a feature of Iomad but I do not believe that different hostnames for different 'companies' is a feature. It was extremely tricky to do as the fixed wwwroot thing permeates Moodle.
Iomad original purpose was for a large training company that offered services to a range of client companies. They wanted each company to have a Moodle completely isolated from each other and have their own custom theme. However, the same course can be provided to multiple companies with each, again, isolated. What it does not do is to give each their own hostname - but this was not a massive consideration.