I buy and sell domain names for a living. I'm pretty sure I would know how Domain Tools works.
The capabilities of their tools make a lot more sense if you gain an understanding of the .com whois database. Domain Tools has no more access than any other Tom, Dick, or Harry with a direct query to whois. The only difference is that Domain Tools has been logging all of their query info for ~6 years. So, for example, they can do a whois history search by looking at their own company database on one domain over previous queries. Also, they can scan their database for all domains owned by a certain company name or email. They can not, however, pull any information out of whois that whois does not have publicly available.
So, I will repeat, if your names have whois privacy from the time of registration, the registry has no idea what your personal information is. As such, it is not available in the whois database, and not available in any Domain Tools search. I hope this makes things easier for you to understand.
I'll sleep well tonight I educated another domain noob while watching my parking stats running up.