Legal aspects of modding.

The support refers to point 3.1, stating that Heroes 5 falls under the category of services, and the new Ubisoft license is general for all products, superseding old licenses.

Perhaps that would be the case if Ubisoft still supported Heroes 5. Although it's debatable.
But there is no more support. The servers are shut down. So, Heroes 5 is a standalone product.
P.S. I can move the discussion to another place to avoid going off-topic.
P.P.S. By the way, I read point 6. It attempts to bring the alienation of copyright under its umbrella:

In this regard, you confirm your agreement that UBISOFT will be the sole copyright holder with respect to the User-Generated Content (UGC) created by you using previously created UBISOFT Content, when and as such UGC is created by you.

This is utter nonsense and does not comply with Russian law.