@Johnny Angell - The first time you add a device you can either manually enter the network information or use a protocol called WPS [Wireless Protected Setup] which securely and automatically transfers the information from the router to the device if both support it.
As others have stated...
Comcast routers [and a lot of others] do this by default but you should have the ability to change it if you prefer. Most modern Comcast routers are built by Netgear.
Most operating systems do that as the OS has no real way of knowing which SSID actually belongs to you. The problem is people are allowing their SSID's to be broadcast, which is a security risk if you don't take other precautions to secure your network.
So you create a name [say for the 2.4G band] and the router automatically replicates it for the 5G band? That's normal enough but not having the ability to modify one without affecting the other isn't.
Apple has always taken the approach of elegance and simplicity over flexibility so I guess...
@DaveF - Are you saying your router doesn't allow separate names for the 2.4 and 5G bands? I've never heard of that before. Are you using a smartphone app to manage the router settings? If so, most have limited feature sets.
Small world. I have an appointment with Comcast tomorrow morning to enable 100 Mbps service.
Did you buy your own cable modem or just the WiFi router? Owning your cable modem will save you money over time as Comcast charges you for it every month.
Unless you're experiencing performance...