Thanks everyone for your thoughts - it is a really fine line, and an on-going issue at this particular venue. I'm generally not one to go behind management's wishes...
It turns out several electricians, the TD, as well as our ME/programmer also forwarded him the schedule so at the very least it's not as if our tech calendar and calls were top secret information. The venue has many grievances filed against them for not following their IA contract, and the steward is keeping a very close eye on their hires/calls.
If you were challenged by management as to why you did an end-around and gave the information to the IA Steward, what would you have said?
Likely a similar answer to yours, in the vein of that a IATSE steward needs to be informed of call times the same as any other crew head to properly account for hours and to avoid overtime.
If only this was the sole issue at the venue, but unfortunately it was just the tip of an iceberg of internal problems. Learned a whole lot about how I like to work, and things I will not do in the future. In retrospect I wish I had directly asked management why the steward was supposed to be off the distribution, but hindsight is 20/20...