What you were expecting to happen, and what actually happened:
Since we’re required to destroy or explode the new heroic gem type, I assumed to be able to select the gem with troops that destroy or explode gems.
How often does this happen? When did it begin happening?
Always and obviously since after weekly reset.
Steps to make it happen again
Try above troops or any that let you select a single gem.
Fun Fact
At least Remove gems doesn’t trigger the effect.
Oh dear, these new gems are really going to mess up Guild Wars! Any troop or gem with a percentage chance, in most cases ends up in the favor of the AI.
This new gem is going to fill the enemy team up more often than the players!
If you explode it it cannot ever fill only their team. It either fills 1-4 of your troops with mana or both teams so if it fills their team it always also fills yours unless the enemy is the one who explodes it.
Trying with Peasant