Chris, I understand that perfectly well. Titles are state issued for registration to use on public roads/ access. If not used on public roads, registration is not enforceable, thus, titling is not a requirement. Titling is a registration event required for use on public lands/ highways.
Bills of sale/ invoices will show chain of ownership, if needed to demonstrate ownership. As we're speaking about race bikes, not used on public roads/ facilities, then no, a title is not needed. A bill of sale would be handy/ smart to get from the previous owner, as well as all previous documents if possible.
There are mixups where even having a title and the vehicle do not denote ownership. One of my bikes, a CR250R that I bought from a friend who had bought it new from Milpitas Honda, had the wrong VIN on the title when it was sold to him new. The dealer had grabbed the wrong MSO out of their drawer/ finance company and titled the bike 1 digit away from his, to him. We discovered this years later and had to go through a massive process to get the names corrected, which eventually involved just doing a lien sale to get things back in order. Of course the only reason to do any of this was to get the bike able for use on public lands.
So while a title is the easiest way to determine ownership (so long as it's not a dupe), it's not the only, nor in the realm of race bikes, standard way to determine ownership...