I think the Lotus Mk6 may also pre-date the ATS ... the first Lotus was built in 1962. But Lotus built only 3 of them. ATS built a whopping 8 to 12 of their cars!
When I wrote the comment about the ATS and the Vallelunga I had just returned from the Concorso Italiano where the Lamborghini guys were claiming the Miura was the first mid-engine road car. My comments were aimed at dispelling their claim.
In order to prove claims like that various authors usually make "qualifications" to their statements, like the first sports car with something larger than 4 cylinders, or the first sports car made in high volume.
In the name of accuracy I need to go back and edit that comment to qualify it, the ATS was the first "Italian" mid-engine road car. Or perhaps I should add a mention of the Lotus and the Djet. There are other parts of that history which need editing as well. I planned to do that when the history is relocated to the web site. All in good time.