Question: The Truth About The "Different Class-C IP Theory" - What do you think?

Note that there are three main reasons to host your sites on different IPs, and you seem to be conflating them

(1) You want different IPs to give you full link juice, if you use these domains to link to each other or other money sites of yours. Lets say you have a choice of 50 backlinks from sites all on the same IP, or 50 backlinks from sites all on different IPs. Everything else is the same. Which do you pick? Hopefully the latter one.

(2) You want different IPs to help prevent Google from seeing the interconnectedness of your sites. Nothing is perfect, but having the more things "unique" about each domain that you interconnect, the less likely Google will be able to connect the dots and potentially de-value or even penalize the sites (to the extent they can for outgoing links). Having your interconnected domains on different c-class domains is just one way to help yo do that.

(3) You do other things on your domains that you think Google potentially might not like. Perhaps you have very thin affiliate sites and you think if Google did a manual review they might zap them. Perhaps you sell links on your domains. perhaps you do cookie stuffing. Who knows. As with #2, the more things "unique" about each domain the better.

Tom

Other than trying to hide nefarious practices as Tom has said, IP diversity will likely give better linkjuice. However, providing you don't overdo it, I think the worst that would happen is Googlebot would assign a similar value to your cross domain links as it would to internal site links under the same domain.