Well, this discipline is designed more for finswimmers than for freedivers. The 50m speed apnea is a very common discipline and it offers a considerable advantage vs. surface sprint - the record is 14.04s vs 15.20s. However, many of the finswimmers are able to pull 100m, so would like to push into this discipline too, where the surface record is 34.79s. The WR for 100m immersion (with a small tank) is 31.52s, so they certainly hope it could be challenged on apnea.
Although the fears about safety are well placed, the discipline is on the WCh just for testing, and I think it is worth of it. If it turns out that it is indeed too dangerous, it won't be accepted.
The finswimming and freediving words are quite separate - I saw it on the French Championship few weeks ago - quite different philosophies, different technique, different public, and very few people active in both areas in the same time (if any at all). So do not think about the 100m apnea as a freediving discipline. It is one for finswimmers.
Results from
Records du Monde - All Finswimming - Toute la Nage avec Palme(s) en France et dans le Monde