Why else do you think they're transitioning to trolly and park table work? It (among other things) is an attempt to mitigate any potential accusations that "sex offenders are knocking on your doors trying to recruit your kids".
I think you are right. If they are sending a known pedophile but according to their 2 witness rule/malarkey unknown to the public to people's doors opens them up for some serious lawsuits $$$. If a pedophile worms his way into a household and molests a child and it is done in the door to door work.
Cart work on the other hand leaves them less likely vulnerable to lawsuits if they instruct the person simply stand there and not engage in extencive conversation and simply direct them to the Organization.