Yes, we are not the only approach. Even when we started collecting data back in 2014 it wasn't the only one. But we did not find any suitable off-the-shelf solution back then.
Homomorphic encryption was discarded because some data to be send needs to be on the clear. For instance a url we need to fetch, so cannot transform it. Also, computationally is very expensive.
Federated learning is actually closer to what we do, take our approach as federated learning where each node is a single user and where all aggregation of records need to happen there, so that record-linkage on the final collector is impossible.
Tomorrow and the day after tomorrow we are releasing the technical details on different blog-posts, this one was more a motivation/introduction to the main dish.