HEAT rounds are based on a very thin jet of molten metal melting through the armour. Making the round detonate a distance from the armour can have a huge effect on its ability to penetrate.

I don’t know enough about explosives to be sure but maybe having that trigger be a little bit further away from the armor makes it significantly more effective, or it’s more of a moral booster, like putting sandbags on tanks.

I guess it’s to tangle / stop the drone from getting too close

Spaced armor and slat armor are also designed to defend against HEAT rounds, protecting vehicles by causing premature detonation of the explosive at a relatively safe distance away from the main armor of the vehicle.

https://en.m.wikipedia.org/wiki/High-explosive_anti-tank#Defense