It's complicated. But: Yes, because FAQ reasons. RAW there's no difference between a Stun Grenade and a Nimbus Grenade that I'm aware of and if it was a Stun Grenade it would certainly be cancelled Probably not (same reason it's not cancelled: because reasons) but RAW Yes.
Not only that, but they are specifically an "Attack": Firing Nimbus Special Ammunition is an Attack. Therefore, you cannot fire them on friendlies in the first place. ...and apparently that's been errata'd to not mean that it gets cancelled! Thanks @ijw.
I recommend reading the fine FAQ, from October 2017... Q: Can weapons with the Impact Template Trait and no value in the damage attribute be fired with allied troops in their area of effect? For example, a Smoke Grenade, an Eclipse Grenade or a Nimbus Grenade. A: Yes.
This might sound like a weird meta-question, but does Attacks per definition count as affecting hostile units for the purposes of FTF? (Can a Zhanying toss a Nimbus on an enemy in order to create a Face to Face as an ARO?)
So apparently the unclear nature of Smoke Grenades as an attack or not can be ignored; we've got this FAQ ruling that can handle it.
I completely forgot about that one, cheera. But it doesn't actually answer the question about whether Nimbus Grenades force a Guts roll (on either enemy or friendly troopers) though.
Given that Redrum isn't FTF with all actions that literally target the trooper performing the Redrum, let's go with 'No'. [emoji14]
I was pulling your leg, but was referring to Data Scan vs a KHD. [emoji14] Serious answer, I'd err to 'No' because the Data Scan makes it clear that the reading of 'affects' for generating FTF is quite narrow.
Yeah, but Data Scan isn't an attack, which is what I'm asking about. I'm fully aware the answer will probably be the same, but Data Scan isn't equivalent.