I've made some sight-seeing module for rockets just for fun, thinking they would boost morale/stats/stress as stated in the wiki.
Unfortunately, dupes return without the bonus and naturally stressed due to low morale, like rocket pilots generally do.
It appears the game does not record dupes as passengers as seen the following images and the attached save file.
Note how the modules are assigned, but the passengers do not appear on the rocket screen. It stays that way also after the rocket is launched.
Once the rocket comes back, dupes fall from the module and do not gain the related bonuses.
Build rocket with sight-seeing module (without gantry). Assign dupes - should fly to the module. Look in rocket screen. Launch. On return, look for the buffs.