[2019] Reg Grenades dont restock Incendiary Grenades?

I just switched to Survivalist and unlocked the Incendiary Grenade which I am really loving. In Roosevelt Island and was tossing them like crazy and eventually ran out. I noticed that when we ran into restock boxes the Grenade symbol would be red, but my Incendiaries count was still 0. Somewhere along the way I did get an extra Incendiary grenade so it must drop from something but the restock boxes don't work for it.

I wanted to confirm that this is how it's supposed to work or is it a bug?

Thanks!

Also, please fix the specialty ammo drops. Collectively we probably killed dozens of NPCs on fire and I manged to get 1 single arrow. I've spec'd out of adding dmg to the specialty weapon bcz it's useless without ammo.