Airfix's workshop blog says:
"an instant collection of impressive 1/35th scale military vehicle kits, these models are being released in partnership with one of our modelling associates, but will be given a distinctly Airfix flavour before they appear on the website and in good model stores everywhere. Benefiting from new box artwork and Airfixised instruction booklets, the initial range consists of 16 tanks and one US tractor"
Does that clear things up or just stir up more mud?
To my mind "instant collection" means the models already exist, and "in partnership with one of our modelling associates" means we got them from someone else. If you know of a 1/35 producer who has 16 tanks and a US tractor in their range you may have solved the mystery.
The blog entry has a painted model of one of the German tanks. Someone might recognise it:
https://www.airfix.com/uk-en/news/workbench/new-2019-airfix-range-unleashed