Let’s not get two scientific with this definition.
A combo guard simply means someone capable of playing both positions .
Virtually every shooter PG was a combo because the skill set at the 2 is much less demanding .
Ricky wasn’t really a combo he couldn’t shoot very well, he was a PG whose defense was so good you could play him at the two because we had enough scoring options and our
one could shoot.
Looking back it’s easier to identify pure two’s
Like ,Lamb, Vital ,or Purvis.
They typically can’t create.
Or in Dysons case his attempted creatively exceeded his skill.
Rip,Caron , and Ray defy description but I like to call them 2/3 ‘s or super two’s
Ryan was a position defier . He had PG ball skills ,could shoot some, but was only a poor passer who improved by his senior year. He typically played the two guard but took the point as a means to rest Bazz without sitting him.
Something Calhoun did with Kamba
The two is a bunch easier to play .