Sorry for the screenshots in Russian, I hope it is clear which meaning I emphasized. Perhaps this is a localization error, but the description says that the structure gives + 5 approval for each unit of the main population.

I do not know what the mistake is, that one does not work or that it gives +5 in the presence of the main population on the planet.
Sorry to write here, but someone is deleting all my posts on the beta test forum.

Wiki has that as:
Sensory Deprivation Resthouse: (Building, non-unique) +5 Approval on System (not per pop) if Riftborn Pop present