Vendee
Aircraft technician and TFO are very different jobs, I'm sure you'll agree. The majority of TFOs I've known would not be shy about commenting directly on anything which was outside normal operations or which they knew to be outside SOP.
Though Sid's link is a little out of date it does list the responsibilities of a training officer, which include:
a) Preparation of a course of ground and flying training for each aircraft type.
b) Line and Area/Role/Route Competency Check (Observer);
c) Emergency and Survival Procedures Check (Observer);
d) role equipment training;
Which indicates to me at least that the three most important areas of training and competency for a TFO, before operating role equipment, are training for each aircraft type (not really necessary if you're simply a pax); line checks as part of a team of three and emergency procedures.
I could never have done your job as an aircraft technician but occasionally flying with a test pilot and flying day after day, night after night as part of a team mean that your professional relationship is entirely different and means that most TFOs would, like you, not ask "are you sure that caption should be lit?" but, nor would they say "I didn't know that caption should be lit"; it's far more likely that they'd point out the caption, ask if the captain required the emergency checklist and then ask, as appropriate, what that meant and what the captain intended to do about it.