These are not different versions. Citi chooses to absorb the cost of one or two guests as a marketing tool. Most card issuers do not.
I'm pretty sure Chase does the same thing as well. I've used my Lounge Club card through my RC card to guest in up to 3 people multiple times and never been charged for extra guests.
It sounds like the only bummer about this offer is the $15,000 minimum CL for the Visa Infinite. I'm hoping my Visa Signature isn't converted to a Visa Infinite if that's the case.