Frozen custard is also often sold as a “concrete”. The difference from ice cream is less in the flavor and moreso in the texture. Concretes hold up better to summer heat. Its more dense than typical ice cream.

A dairy queen blizzard is probably also a frozen custard, not typical ice cream, as they had the whole “it wont fall out if you flip it upside down” thing just like they do at some frozen custard places