Dataset used for regression
Sorry I'm not going to read the paper, but in general it's perfectly possible to use binary values 0/1 as numerical regression targets. A regression model doesn't care about having a continuous sample in the training set, it just calculates the relationship between the features and the target variable. For example a linear regression needs only two points to learn a model in theory. Of course this doesn't work if there are specific patterns either between the two target values or outside them, the model can only generalize on the full continuous range. As a result it will mostly predict values in the range [0,1] but it can also predict values outside of it.