I can confirm that sFTP Adapter is not showing as separate status group in messages statuses tab on PI 7.4 SP 7 AEX. We have deployed the sFTP Adapter.
However, I didn't have the chance to try this out as we are still in process of switching from old PI 7.0 environment to new environment, hence no sFTP scenario on new PI yet.
Maybe you wanna clarify with SAP if this is a missing feature or if this is cumulated under "File Adapter" (unlikely in my opionion)
Cheers
Jens