Hey I got one right for a change?
Regarding shorting secondary coils, I think this will result in a higher primary current going in. Instead of building current to saturate the coil and then levelling out on primary resistance, it also now has to supply the secondary which takes current whilst charging (when is shouldn't). I don't know the exact characteristics of these things, but short on a secondary means increased current on the primary. I'm also not sure what the current does when when the transistor goes off with a shorted secondary. It probably reduces and if so, not a problem. Surprisingly I can't find this kind of measurement on the web.
Since the primary probably current goes up and the transistor has fixed instantaneous and long term limits; it may fail immediately or after several cycles depending on components. Contacts are harder to break - they would normally weld in after abuse in say a relay, except this big cam comes and forces them open rather than a spring.
I'd be interested if someone has a graph of primary vs secondary currents when normally loaded AND when the secondary is shorted out. I think it goes up in a nasty way whilst saturating.
EDIT:- I found something, but on modern transistor ignitions which will have protection (current limit). But yes, a shorted secondary makes the average current in the primary go up. Enough to blow up one of our simple transistor ignitions? I don't know.