I think it is because the proprietary part for them is the data, not the particular algorithm. They benefit more from other people making advances on their tech

I think it is because the proprietary part for them is the data, not the particular algorithm. They benefit more from other people making advances on their technology because they have the data to get more benefit than anyone else. If they kept it to themselves, they would get no "free" advancement. So they trade-off the secret of the technique in the hope that others will advance the technique, making their data more valuable.