[2.4.4] Force Merge API usage

[s925484h]

In ES 2.x, was it a bad idea to use the Force Merge API? I have found the danger alert only in the of the latest versions of ES docs.
In particular, this ES cluster is running version 2.4.4 and has a cron job that each night runs the following script:

1. Search with the Scroll API on all indices all the documents with _ttl < current time in ms
2. Delete all the hits in the current Scroll via the Bulk API, repeat until the Scroll search does not return more hits
3. Delete the scroll
4. Set index.ttl.disable_purge to false, wait 20 minutes then set it to true
5. Call the Force Merge API first with the parameters only_expunge_deletes=true&max_num_segments=20, wait 5 minutes then call it again with max_num_segments=20`.

This was set up by another person that previously managed the cluster, and I would like to know the implications of running the above script daily and if somehow can hinder the performance/health/disk usage of the cluster.

Thanks in advance.