I think the only limiting factor is the softwar default to one digit on Lan IP address issuance?
.1 results in 10 devices max..
No, that is not the reason. TWC codes a maximum number of simultaneous DHCP connections into their leased routers. Those TWC or Spectrum commercials you see showing more than a dozen users all getting web access while visiting their neighbors are quite misleading.
There's also a related issue - many Apple devices (both phones and network devices) don't behave well with just a single digit in the last segment of the IP address. That's why we tell folks to program their routers to begin DHCP at 11 rather than 1. If you bought your own Arris, they default to 32 DHCP addresses on subnet 192.168.1 running from 11 to 42