Potentially it's being poorly described by the writer.
Tanks have comparatively weak turret and upper armour. Plus you don't need to destroy a tank to reduce its combat ability, you can just make it throw a track, or destroy its external sensors. A grenade will sometimes do that, but even better is a cheap rocket propelled grenade warhead that you drop onto the turret of the tank, as those are designed to penetrate armour.
In addition, russian tanks would be driven with their hatches open for fresh air, providing an easy entry point for a skilled Ukrainian drone pilot.
Tanks have comparatively weak turret and upper armour. Plus you don't need to destroy a tank to reduce its combat ability, you can just make it throw a track, or destroy its external sensors. A grenade will sometimes do that, but even better is a cheap rocket propelled grenade warhead that you drop onto the turret of the tank, as those are designed to penetrate armour.
In addition, russian tanks would be driven with their hatches open for fresh air, providing an easy entry point for a skilled Ukrainian drone pilot.