Tease - this probably isn't going to help make your day
but the main reason for not accepting the subdomain sites is that on average, 80% of them are used as a "scamming" method by some overseas WMs, and tend to redirect within a few weeks. To avoid having to go back and remove those links every day, we choose to just not list them.
On the bright side, there are one or two submitters that have emailed WMs of LLs and "arranged" the ability to submit subdomains