Hi milktea.
And that's the primary difference between you both. You have locked up your emotions so tight, Houdini couldn't get in, and that's not good for you. Part of transition entails you learning to cope with, and understand an entirely new set of emotional cues and responses.
Yours parents are first and foremost basically emotional creatures when it comes to caring for their offspring. Logic and rationale will come much later. So YOU need to take that into major consideration in your emotionless though processes and try to perceive the hurt your parents will FEEL, if not told before hand.
Having reread your first paragraph I'm really overwhelmed at the total disconnectedness or disassociation your perceive the simple task, Love calls for, in telling those near and dear, of a major change in your life circumstances. To the point I'm worried about you.
Parenting has NO "cost benefit ratio", nor does it have "tedious aftercare functions". The love a parent should have for their son or daughter transcends ALL logic, reasoning, rationale,function, etc, etc. It's just plain and simple "move mountains" LOVE. Needs no further explanation or description.
Could I further suggest, you stop asserting your preconceptions of fear and helplessness onto people you clearly love and care for you. Nobody, none of us have the slightest idea, how another loved one will take and react to any news we have for them. It's only after they have processed there understanding and knowledge of the situation, will you ever find out how they really thought about it.
Tell them; and let them work out and process the best response they understand. And please talk to your therapist about why you have repressed your feelings. It's not normal or wholesome.
Huggs
Catherine