The Hidden Blade doesn't trigger "Trigger a fire spell on hit" if no command was issued lately

Unseen Strike from The Hidden Blade doesn't trigger "Trigger a fire spell on hit" if no user input was issued lately

Reference number: 4256202055

When equiping a weapon with "Trigger a Socketed Fire Spell on Hit, with a 0.25 second Cooldown" as a main hand and using The Hidden Blade on off hand, Unseen Strike should be hitting with main hand thus trigger the fire spell socketed into it.

But when no new user input (any skills, or left click move counts) was made in past few seconds, it will stop triggering the spells.

Holding down left mouse button (moving) doesn't refresh as a new user input.

Video proof: https://youtu.be/rfjKG7zCFIM