I understand it's frustrating, but the license is there for an entirely different purpose, same with the email. Not to be heartless, but if they took the time to read the license, I would hope they understand then what the license is actually for any why emailing the person at the end is not a good idea for solving a problem related to a product that is not the licensed product. They're building up hope for themselves and then just getting themselves frustrated when it turns out they made a mistake, and that's not really fair on the licensee's part, especially when service manuals in the car are usually pretty clear on the means for support.
My last job was managing the support for a smaller university, and every so often we'd get people who just searched "Help Desk" and somehow stumbled onto our University Help Desk phone number. They'd get insanely frustrated when, rather often, we were completely unable to help them because the product was too niche or specific for my technicians to even begin to know how to troubleshoot; we had low enough call volume that the free publicity for the school after helping strangers more than offset the time spent solving a problem that wasn't ours to solve. But when the callers would get really upset and disgruntled, I'm not entirely sure what they expected, especially since my technicians would make it perfectly clear that we weren't a generic Help Desk, we were specific to a university. I have plenty of sympathy for them not being able to get good support through the correct channels, but when you know you're not at the right place and just hoping, it doesn't seem fair to peg blame on the people you know are the wrong people to contact.
Edit to reflect your edit:
I would imagine that the part that reads "THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,..." should give away that this is not for support. Also that it doesn't read like a support document at all, and that it's not included in the car's support manual, and that the email doesn't mention Toyota at all. If they email that address from that page, they're not reading the file, they're just scanning for an email address. I'm not saying people who do this are idiots or anything of the sort - as someone who loves helping with tech issues, I sympathize and even empathize after having crap service from many companies. But the people are creating their own disappointment.