The cables are the least of your worries for differences between the radios. Many of the cables can be used for many radios. Cables are designed based on the manufacturer's requirements for connector at the radio, required electronics (some are 2 wire interface and others are three) and wiring on said connector (some are wired shield and tip while others are wired shield and ring). There is a lot we keep up with and have to figure out long before we first address a radio.
Now let's talk about the programming process. While there are likenesses in the radios (Receive and transmit frequencies, operating mode, skip and others), there are far more differences. The programming process flashes ALL of the elements of the radio, not just what is common between models. So given the two radios for this example, what would the program do with all the DSTAR settings in the IC-2820 when the FT-65 does not have those features (trash them and therefore trash the radio???) Do you not want to be able to set dual tones (different for transmit and receive tones) in the FT-65 just because the IC-2820 does not have that ability? Do you not want to be able to put a memory channel in all of the banks as in the FT-65 and just limit you to one bank for one channel as in the IC-2820.... what a loss of functionality?
Do you want a piece of software in which you must discern what works for your radio and what does not.... we could put all 100+ columns on the spread sheet and 1000+ features in the settings file and you could work through them to figure out what applies to your radio and what does not... what fun.
No, we at RT Systems have worked for 26 years, since we invented this process in 1995, to give you a program that is specific to a radio. One that helps you know what you radio can and cannot do. One that is a reflection of your radio without the black box and without making you wade through things that don't apply. One in which when you set a feature, you can check that it is set to your selection through the corresponding menu item in the radio.
With that said, remember, there is copy and paste between the memory sheets of the programmers, even those with different options from different manufacturers. The programmer will take care of the "likes" and "differences" to make set up of multiple radios as easy as possible.