Customers only need to place backorders on one site.
NameJet and SnapNames domain name inventory is being integrated so that both platforms have the same inventory.
Web.com now owns both domain marketplaces, so it makes sense for the inventory to show on both sites. Any registrars that have direct-transfer expired domain deals with SnapNames will now also be on NameJet.
This is somewhat similar to the change the sites made in 2016 when they teamed up (pre-acquisition) to go after pending delete domains.
With this update, someone with accounts on both platforms can bid against themselves. It no longer makes sense to bid on both platforms, so customers should only place backorders on a single platform.
Over time, I expect one of the platforms to be deprecated or for Web.com to launch a singular marketplace.